125
b.
64
112
111
70
a.
b.
c.
d.
116
a.
b.
c.
d.
115
a.
b.
c.
d.
100
126
103
77
a.
b.
58
36
35
1
a.
b.
70
69
b.
76
Which of the following materials has nearly zero temperature coefficient of resistance?
carbon c. copper
porcelain d. mangarin
Which of the following materials has a negative temperature coefficient of resistance?
brass c. aluminum
copper d. carbon
Which of the following statement is true both for a series and a parallel DC circuit?
powers are additive
voltages are additive
currents are additive
elements have individual currents
The superposition theorem is essentially based on the concept of:
duality c. reciprocity
linearity d. non-linearity
When current flows in a conductor, heat is produced because:
heat is directly proportional to the square of the current
of electronic collision
of interatomic collision
of Joule s law
Ohm s law can be applied with certain reservations to:
rectifying devices c. electrolyses
semiconductors d. thermionic valves
The presence of an electric current is made known by
flashing c. cracking
effects produced d. electric shock
International ohm is defined in terms of resistance of
a column of mercury c. a unit length of metal wire
a cube of carbon d. a cube of copper
The capacitance of a capacitor is NOT influenced by
plate thickness c. plate area
plate separation d. nature of the dielectric
A capacitor consists of two
insulators separated by a dielectric
conductors separated by an insulator
ceramic plates and one mica disc
silver coated insulators
Point out the WRONG statement
The magnetizing force of the center of a circular coil varies a. directly as the number of its turns
directly as the current
directly as its radius
inversely as its radius
Permeability in a magnetic circuit corresponds to _______ in an electric circuit
conductivity c. conductance
resistivity d. resistance
A material commonly used for shielding or screening magnetism is
brass c. copper
aluminum d. soft iron
Iron becomes magnetized by induction when it is
heated
suspended east and west
near to one end of a magnet
treated with some chemicals
The relative permeability of paramagnetic substance is
slightly less than 1 c. slightly greater to 1
equal to 1 d. very much greater than 1
Which of the following materials does not have permanent magnetic dipole
paramagnetic c. diamagnetic
antiferromagnetic d. ferromagnetic
Which of the following materials is used for making permanent magnets a. carbon steel
platinum cobalt
alnico V
all three mentioned above
The direction of induced emf can be found by
Lenz's law c. Kirchhoff s voltage law
Fleming s right-hand rule d. Laplace s law
Point out the wrong statement
Magnetic leakage is undesirable in electric machines because it
leads to their increased weight
increases their cost of manufacture
produces fringing
lowers their power efficiency
If a current of 5A flowing in a coil of inductance 0.1H is reversed in 10ms, emf induced in it is ________ volt.
100 c. 1
50 d. 10,000
Permanent magnets are normally made of
aluminum c. cast iron
wrought iron d. alnico alloys
Those magnetic materials are best suited for making armature and transformer cores which have _______ permeability and _______ hysteresis loss
low, high c. low, low
high, low d. low, high
Ferrimagnetic materials generally behave as a
semi-conductor c. insulator
conductor d. any of a, b, or c
Eddy current loss can be minimized by
decreasing the resistance of magnetic medium
increasing the resistance of magnetic medium
decreasing the permeability of magnetic medium
none of these
A collapsing field around a coil
tends to opposed the decay of coil current
helps the decay of coil current
tends to aid current flow reversal
does not effect the coil current flow
The capacity of a lead-acid cell does not depend on its
rate of charge c. temperature
rate of discharge d. quantity of active material
Trickle charging of a storage battery helps to
prevent sulphation
keep it fresh and fully charged
maintain proper electrolyte level
increase its reserve capacity
A dead storage battery can be revived by
a dose of sulfuric acid
adding so called battery restorer
adding distilled water
none of the above
The growth of current in an inductive circuit follows
hyperbolic law c. exponential law
ohm s law d. linear law
It is difficult to magnetize steel because of its
low permeability c. high permeability
high retentivity d. high density
Hysteresis losses can be reduced by
Using grain-oriented silicon steel
Increasing the frequency of the field
Laminating the core
None of these
The unit of field intensity is
coulomb c. newtons/coulomb
coulomb/m2 d. none of the above
Dielectric strength of a material depends on
moisture content c. temperature
thickness d. all of the above
If a dielectric is placed in an electric field, the field strength
decreases c. remains the same
increases d. becomes zero
The KW-hr meter can be classified as a/an _____________ instrument
deflecting c. recording
digital d. indicating
The moving system of an indicating type of electrical instrument is subjected to
a deflecting torque c. a damping torque
a controlling torque d. all of the above
The damping force acts on the moving system of an indicating instrument only when it is
moving c. near its full deflection
stationary d. just starting to move
Which of the following ammeter will be used to measure alternating currents only?
electrodynamic type c. induction type
permanent magnet type d. moving-iron
The condition of a liquid electrolyte is measured in terms of
its
current value c. acid content
specific gravity d. voltage output
The two main defects of the primary cell are
polarization and sulphation
local action and polarization
buckling and polarization
sulphation and buckling
One advantage of a secondary cells is that it
can be easily recharged
can be sued for portable equipment
it is compact, easy to carry
cannot be recharged
Electrolyte of a storage battery if formed by adding
water to hydrochloric acid c. hydrochloric acid to water
sulfuric acid to water d. water to sulfuric acid
Induction instrument have found widest applications as
voltmeter c. frequency meter
ammeter d. watthour meter
Induction watthour meters care free from ________ errors
phase c. temperature
creeping d. frequency
Maxwell-Wien bridge is used for measuring
capacitance c. inductance
dielectric loss d. phase angle
The capacitance and dielectric loss of a capacitor is generally measured with the help of _________ bridge
De Sauty c. Wien series
Schering d. Anderson
The output voltage of a single loop generator is a
steady dc c. pulsating dc
steady ac d. pulsating ac
Electric dc generators have normally, an overall efficiency of the order of
60-80% c. 80-90%
75-85% d. 85-95%
The armature magnetic field has effect that
it demagnetizes or weakens the main flux
it cross magnetizes, or distorts it
it magnetizes or strengthens the main flux
(a) and (b)
In a dc generator, the flux seem to be ______ at the trailing pole tips and also _________ at the leading pole tips
weakened, weakened c. crowded, weakened
weakened, crowded d. same, same
Electric power is almost exclusively generated, transmitted and distributed by three phase system because it a. is more efficient
use less material for a given capacity
costs less than single phase apparatus
all of the above
Interpoles are normally connected in
parallel with the field c. parallel with the load
series with the field d. series with the load
Carbon brushes are used in electronic motors to
brush off carbon deposits on the commutator
provide a path for flow of current
prevent overheating of armature windings
prevent sparking during commutation
If positive phase sequence of a 3 phase load is a-b-c, the negative sequence would be
b-a-c c. a-c-b
c-b-a d. all of the above
Power factor improvement
does not effect the performance characteristics of the original load
employs series resonance
increases the active power drawn by the load
increases the reactive power taken by the load
The chief disadvantage of a low power factor is that
more power is consumed by the load
current required for a given load power is higher
active power developed by a generator exceeds its rated output capacity
heat generated is more than the desired amount
In the two-wattmeter method of measuring three-phase power, the two wattmeter indicate equal and opposite readings when load power factor angle is ____ degrees lagging.
60 c. 30
0 d. 90
When phase sequence at the three-phase load is reversed
phase powers are changed
phase currents are changed
phase currents change in angle but not in magnitude
total power consumed is changed
The method of symmetrical components is very useful for
solving unbalanced polyphase circuits
analyzing the performance of 3-phase electrical machinery
calculating currents resulting from unbalanced faults
all of the above
There are no transients in pure resistive circuits because they
offer high resistance c. have no store energy
obey ohm s law d. are linear circuits
The current flowing in the conductors of a DC motor is
AC c. AC as well as DC
DC d. transients
The torque of a motor is
the force in N-m acting on the rotor
the product of tangential force on the rotor and its radius
the electrical power in kW
the power given to load being driven by the motor
The speed of a series motor at no load is
zero c. 3600 rpm
3000 rpm d. infinity
If the back emf in a DC motor is absent, then
motor will run at very high speed
motor will run at very slow speed
motor will not run at all
motor will burn
For both lap and wave windings, there are a many commutator bars as the number of
poles c. slots
armature conductors d. winding elements
The only function of dummy coils in a dc armature winding is
to
increase the induced emf
render the average pitch an integer
provide mechanical balance to the armature
modify its electrical characteristics
Lap winding is suitable for __________ current, _________ voltage dc generators
high,low c. low, low
low, high d. high, high
The series field of a short-shunt dc generator is excited by
_________ current
shunt c. load
armature d. external
Armature reaction is attributed to
the effect of magnetic field set-up by the armature current
the effect of magnetic field set-up by field current
copper loss in the armature
the effect of magnetic field set-up by back emf
If the resistance in a series RC circuit is increased, the magnitude of the phase angle a. increases
remains the same
decreases
changes in an indeterminate manner
The current in RLC series circuit, i.e. at resonance is
maximum c. infinity
minimum d. zero
At a frequency less that the resonant frequency
series circuit is capacitive and parallel circuit is inductive
series circuit is inductive and parallel is capacitive
both circuits are inductive
both circuits are capacitive
In dc generators, armature reaction is produced actually by
its field current
armature conductors
field pole winding
load current in armature
Shunt generators are most suited for stable parallel operation because of their ________ voltage characteristics
identical c. linear
drooping d. rising
Two parallel shunt generators will divide the total load equally in proportion to their kilowatt output ratings only when they have the same
rated voltage c. internal laRa drops
voltage regulation d. both (a) and (b)
The main function of an equalizer bar is to make the parallel operation of two over-compounded dc generators
stable c. regular
possible d. smooth
A coil with large distributed capacitance has a
low resistance
low Q
low resonant frequency
high resonant frequency
Which if the following is not a non-linear element?
diode
transistor
heater coil
electric arc with unlike electrodes
For maximum power transfer, according to maximum power transfer theorem, source impedance
must be very much large as compared to the load impedance
must be complex conjugate of load impedance
must be equal to load impedance
must be very small as compared to the load impedance
Ideal transformer assumptions do not include
zero reactance of windings
zero resistance of windings
no leakage flux
no saturation of core
If residual magnetism of a shunt generator is destroyed accidentally, it may be restored by connecting its shunt field
to earth c. in reverse
to an arc source d. to a dc source
An ideal generator is one that has __________ voltage
regulation
low c. positive
zero d. negative
The __________ generator has poorest voltage regulation
series c. shunt
compound d. over compound
The counter emf of a dc motor
often exceeds the supply voltage
aids the applied voltage
helps in energy conversion
regulates its armature voltage
The resistance of low voltage side of a transformer
is equal to resistances of its high voltage side
is more than resistance
is less than the resistance of its high voltage side
(b) or (c)
What type of core is used for a high frequency transformer?
air core c. aluminum core
closed iron core d. open iron core
In any transformer the voltage per turn in primary and secondary remains
always different c. always in ratio K
always same d. sometimes same
The size of a transformer core will depend on
frequency
flux density of the core material
area of the core
both (a) and (b)
Under constant load conditions, the speed of a dc motor is affected by
field flux c. back emf
armature current d. both (b) and (c)
A series motor is best suite for driving
lathes c. sheares and punches
cranes and hoists d. machine tools
The shaft torque of a dc motor is less that it armature torque because of _____________ losses
copper c. iron
mechanical d. rotational
The speed of a dc motor ca be controlled by varying
its flux per pole
resistance of armature circuit
applied voltage
all of the above
High speed alternators have a rotor construction
similar to dc machines c. of salient type
of non-salient type d. none of the above
Distributing the armature winding of alternator in more than one number of slots per pole phase results in
reduction of irregularities produced in waveform
economy of materials used in winding
less weight of the entire armature
increase of generated emf per phase
When the power factor of load is unity, the armature flux of an alternator will be
demagnetizing c. cross magnetizing
square wave form d. none of these
The maximum current that can be supplied by alternator depends upon the
strength of the exciter voltage
number of poles
strength of the magnetic field
maximum heat dissipation
Controlled rectifiers employ
diodes c. bridge circuits
thyristors d. both (a) and (b)
When a 400Hz transformer is operated at 50Hz, its kVA rating
is
reduced to 1/8 c. unaffected
increased 8 times d. increased 64 times
The primary and secondary windings of an ordinary 2-winding transformer always have
different number of turns
same size of copper wire
a common magnetic circuit
separate magnetic circuits
At relatively light loads, transformer efficiency is low because
secondary output is low
transformer losses are high
fixed loss is high in proportion to the output
Cu loss is small
Adjustment of field excitation on one of the two alternators operating in parallel will
increase its load c. decrease its load
change in frequency d. change its power factor
Synchronizing motors are
self-starting c. essentially self-starting
not self-starting d. none of these
A 3 phase synchronous motor is running clockwise. In case the direction of its field current is reversed
the motor will continue to run in the same direction
the motor will run in the reverse direction
the motor will stop
the winding of the motor will burn
The all-day efficiency of a transformer depends primarily on
its copper loss c. the duration of load
the amount of load d. both (b) and (c)
The essential condition for parallel operation of two single phase transformers is that they should have the same
polarity c. voltage ratio
kVA rating d. percentage impedance
Instrument transformers are used on ac circuits for extending the range of
ammeters c. wattmeters
voltmeters d. all of the above
The principle of operation of a 3-phase induction motor is most similar to that of a a. synchronous motor
repulsion-start induction motor
transformer with a shorted secondary
capacitor-start, induction-run motor
When a 3 phase synchronous generator is supplying a zero pf lagging load the armature field affects the main field in the following way
directly opposes it c. augments it directly
cross-magnetizes it d. none of the above
Improvement in the power factor in an induction motor
decreases torque
increases the torque
increases the current
increases the torque and decreases the current due to increased impedance
Short circuit test on the induction motor can be used to find out
the transformation ration of the impedance motor
power scale of circle diagram
copper losses in the induction motor
all of the above
If the air gap of the induction motor is increased
the magnetizing current will decrease
the magnetizing current will increase
the power factor will decrease
none of the above
If starting winding of a single phase induction motor is left in the circuit, it will
draw excessive current and overheat
run slower
run faster
spark at light loads
If a single phase induction motor runs slower than normal, the more likely defect is
improper fuses c. open starting winding
shorted running winding d. worn bearings
A permanent split single-phase capacitor motor does not have
centrifugal switch c. squirrel-cage rotor
starting winding d. high power factor
Zero power method of an alternator is used to find its
efficiency c. armature resistance
voltage regulation d. synchronous impedance
Is a device which functions on failure of the insulation of a machine, transformer or of other apparatus to ground or on flash over of a dc machine to ground
overhead ground relay c. grounding reactor relay
ground insulation relay d. ground protective relay
Is an equipment which controls the gate or valve opening of prime mover
silicon controlled rectifier c. rheostat
contactor d. governor
Is the mechanism which is used for moving a removable circuit breaker unit to end from the connected, disconnected and test positions
permissive control device
notching device
blocking device
position changing mechanism
Is the complete electrical mechanism or servo-mechanism including the operator motor, solenoid, position, switches, etc., for a tap change, induction regulator or any piece of apparatus which has no device function number
regulating device c. rotating device
reversing device d. operating mechanism
Is use to increase or decrease in one step the value of field excitation on a machine a. tripping relay
field regulator
DC reclosing relay
field changing contactor
A special type of diode used to regulate dc voltage supply
Thyristors c. Diac
Zener d. Shockley
Electrons normally flow
from the grid to the plate of an electron tube
from the positive terminal to the negative terminal inside the battery
through a capacitor
at the speed of light in a conductor
When an electric current is flowing in a conductor, heat is developed at a rate proportional to the square of the intensity of the current. This relation is known as
Coulomb s law c. Faraday s law
Joule's law d. Ohm s law
An electric device designed to receive electrical power from a dc source and deliver alternating power without the aid of external source of alternating voltage
amplifier circuit c. rectifier circuit
oscillator circuit d. integrated circuit
The modulated wave is transmitted over lines or space. However at the receiving end, the signal wave must be recovered again by means of electronic circuit called a. frequency changer c. filter
b. detector d. inverter
Process by which the characteristics of a wave is varied as a function of the instantaneous value of another wave
detection c. phase shifting
modulation d. feedback
In any network consisting of linear impedances, the current at any point is the sum of the currents that would flow if each generator were considered separated all other generators being replaced at the time by impedances equal to their internal impedances. This principle is known as
Kirchhoff s law c. Thevenin s Theorem
Superposition Theorem d. Reciprocity Theorem
When the emfs in the two windings of the transformer are opposite in direction, the polarity is
positive c. additive
negative d. subtractive
For a transducer, the impedance which will simultaneously terminate all of its inputs and outputs in such a way that each of its inputs and outputs, the impedances in both directions are equal are called
iterative impedances c. characteristics impedances
image impedances d. driving impedances
To determine the equivalent resistance of an inductive motor, we use
no load test c. blocked rotor test
short circuit test d. polarity test
Consisting of a single rotating machine that is mainly to convert alternating current to direct current
motor generator set c. rotary converter
motor converter d. mechanical rectifier
It is the ration of lumens reaching the work plane by the total lumens generated by lights
maintenance factor c. coefficient of utilization
room ratio d. room index
Intermittent operation in which the load conditions are regularly recurrent
short time duty c. periodic duty
continuous duty d. varying duty
In a dc machine, this consists of coils placed at the neutral point midway between the main poles
compensating winding c. interpole winding
equalizer winding d. neutralizer winding
A connection to ground for one or more non-carrying metal parts of the wiring system or apparatus connected to the system
system ground c. equipment ground
system neutral ground d. capacitive ground
A transformer intended primarily to provide neutral point for grounding purposes
ground regulating transformer
ground equalizer transformer
grounding transformer
ground fault transformer
A grounding transformer may be connected zigzag of
delta-delta c. wye-delta
delta-wye d. wye-wye
Of the lighting arresters sold in the market, which can handle much surge current and excessive contamination of dirt a. distribution arrester c. station arrester
b. line arrester d. intermediate arrester
It is a disruptive discharge between electrodes of measuring gap, voltage control gap, or protective device
flashover c. sparkover
corona d. fireover
The voltage that insulation is capable of withstanding without failure or disruptive discharge when tested under specified conditions
maximum withstand voltage
rated withstand voltage
c. critical withstand voltage
minimum
In symmetrical components, the components consisting of balanced 3 phase vectors and having a phase sequence opposite to that of the given vector is a. additive sequence system
subtractive sequence system
negative sequence system
positive sequence system
The fault current that exists immediately after the fault is known as
transient current c. subtransient current
steady state current d. sustained current
The insulation strength of an equipment is described as its
basic insulation strength c. basic insulation level
basic impulse stress d. basic insulation factor
In hydroelectric power plant, it is used to prevent the sudden rise and drop of water pressure.
penstock c. dam
intake tower d. surge tank
To test the accuracy of a kilowatthour meter an electrician used a wattmeter. He found out that the meter makes 5 revolutions in 18 seconds. The meter constant is 3.2. What is the percent error if the wattmeter reading is 3,368?
8% slower c. 5% slower
8% faster d. 5% faster
A 100 MW power plant burns 0.4 kg of coal with heating value of 7.2 x 106 calories per kg to produce 1 KwHr. If the power plant acts as a base load, how many tons of coal per day is consumed if the power plant operates 24 hours per day?
530 c. 830
960 d. 260
An amplifier has an output of 50 watts. What is its output in dbm?
47 c. 75
50 d. 80
How is the storage battery rated in capacity?
volts c. amperes
watts d. ampere – hour
The basis where the flow of current is from positive to negative was derived from _____
superstition c. scientific
tradition d. convention
A 220 volts dc series motor when running at 800 rpm draws a current of 100 amperes. The combined resistance of the armature and the field is 0.1 . What is the speed when the motor develops one – half of the original torque?
1,600 rpm c. 1,147 rpm
1,690r pm d. 1,225 rpm
The fault current that exists immediately after the fault is known as:
sub – transient current c. steady – state current
transient current d. sustained current
Its primary function is to provide ground source
zig – zag transformer c. surge arrester
sectionalizer d. tertiary transformer
The following are the given loads of a particular circuit:
5 – 15 hp motors
3 – 5 hp motors
8 kw – lighting loads
3.5 kw – miscellaneous loads
Calculate for the maximum demand if the demand factor is 65%.
78.64 c. 51.12
45.81 d. 120.98
An SCR s three leads are the:
anode, cathode and emitter
anode, cathode and gate
base 1, base 2, and emitter
main terminal 1, main terminal 2, and gate
A 20 kv/7.87 kv autotransformer has a secondary line current of 100 A. What is the current in the common winding?
139.25 A c. 60.65 A
100 A d. 39.35 A
A 220 volts single – phase induction motor draws current of 10 amperes at 0.75 power factor. A capacitor of 50 µF is connected in order to improve the power factor. What is the new power factor?
0.866 leading c. 0.95 lagging
0.866 lagging d. 0.95 leading
A 3Φ 220 volts, 10 hp induction motor having a power factor of 0.8 has 3% losses. Determine the current drawn by the motor.
25.23 A c. 20.18 A
43.69 A d. 14.56 A
A solenoid having an inductance of 12 henry is impressed across a voltage source such that the current through it is 3 amperes. What is the average voltage at t = 0.2 sec?
150 volts c. 120 volts
180 volts d. 220 volts
An electric heater takes 23.889kcal in 20 minutes at 200 volts. What is the current drawn by the heater?
8.4 A c. 1.67 A
16.67 A d. 0.42 A
A series RLC circuit has a resistance of 15 and an inductive reactance of 1,500 . What is the Q – factor of the circuit at resonance?
120 c. 140
100 d. 150
A synchronous motor that is used for power factor correction only.
synchronous reactor c. generator
alternator d. synchronous condenser
Why are transmission towers sometimes constructed in lattice type and sometimes in pole type although they have the same capacity and voltage rating?
reliability c. right of way
wind load d. safety
The capacitive reactance of a transmission line is 90,000 ohms per kilometer. Find the total capacitive reactance if the transmission line is 50km long.
4.5x 106 c. 90,000
1,800 d. 180,000
An 80 µF capacitor in series with 1,000 resistor is connected suddenly across a 110 V supply. Find the rate at which current begins to decrease.
13.75 A/s c. 1.375 A/s
0.1375 A/s d. 137.5 A/s
A 100 watts 230 volts gas fitted lamp has a mean spherical candlepower of 92. Find its efficiency in lumens per watt.
11.56 c. 115.6
1.156 d. 1,156
Charges that are both positively and negatively charged are called:
negatron c. neutron
neutraton d. positron
With the primary of CT energized, the secondary must never be made open to prevent this to happen. a. build up of magnetic bias
burning of primary winding
burning of secondary winding
absence of induced voltage
A 25 miles (40 km), 3Φ, 3 wire sub transmission line with an impedance per conductor of (7.65 + j16.52) is supplying a balanced 3Φ load of 4,000 kw, 33,500 volts line to line, 60 hz at 0.8 p.f. lagging. The conductors used in the line are 336.4 MCM, ACSR, 26/7 strands vertically spaced 4.5 ft apart. If a 2,100 kvar, 3Φ pure capacitor bank is installed across the load, what is the voltage dip maintaining 33,500 volts at the receiving end?
735 V c. 585 V
635 V d. 485 V
A symmetrical cable with 200 meters span has a unit weight of 2 kg-force per meter uniformly distributed along the horizontal. The tension at the lowest point is 2,000 kg-force.
Find the tension at the supports in kg-force.
2,010 c. 4,080
2,040 d. 2,000
The positive-sequence components of the system has
the same phase-sequence as the original
the opposite phase-sequence as the original
zero-phase displacement
both a and b
A voltmeter rated 150 volts has an internal resistance of 10 k . What resistance should be added in series to the internal resistance so that the voltmeter will register full scale deflection across 450 V?
6.67 k c. 40 k
30 k d. 20 k
Pilot lamp in a MCC indicates a motor control center
underload
overload
normal condition of the load
out of order
A south pole 20 unit pole is placed one inch away from another south pole 35 unit pole. What is the force between the two poles?
108.5 dynes repulsion c. 70 dynes repulsion
108.5 dynes attraction d. 70 dynes attraction
In a 34.5 kv three-phase system, the Thevenin s equivalent impedances are
Positive impedance, Z1 = 0.015 p.u. at 50 MVA
Zero impedance, Z0 = 0.03 p.u. at 50 MVA
What is the phase to phase fault current?
48,000 A c. 8,400 A
80,000 A d. 32,000 A
This is an electrically operated switch which is rated in amperes and is also used in overload protection of motors. a. magnetic starter c. magnetic contractor
b. safety switch d. manual starter
These are high intensity discharged lamps which are usually installed in outdoor and wide areas and are mounted on poles whereas for indoors these are used for high ceiling applications.
surfaced c. low mount
recessed d. high bay
What do you call an insulated conductor that can be used only up to 300 volts and is considered having no insulation base on general rating?
insulated conductor c. enameled conductor
base conductor d. covered line wire
What is the field intensity E in millivolts per meter of an omnidirectional antenna over a distance of 1 km if the power is 1 kw? (impedance of free space is 120 )
153.4 c. 120
150 d. 173.32
A limit switch is used to shut off the power when _____ a definite limit.
current exceeds c. the travel reaches
voltage falls below d. frequency exceeds
A magnetic circuit consists of silicon steel of 2000 permeability of 10 cm length and cross sectional area and of 1 centimeter length. A one – ampere current flows through 500 turns of coil. Calculate the field intensity across the air gap.
622 Oersted c. 590 Oersted
755 Oersted d. 350 Oersted
Find the GMD of a double circuit having vertical configuration 3 meters apart and 3 meters between conductors. The phase configuration of the 1st circuit is ABC from top to bottom and the 2nd circuit is CBA.
4.24 m c. 3.567 m
3.78 m d. 3 m
A relay coil carries a polarizing current of 1 A dc and a signal ac current of 3 A at 50 hz. If coil resistance is 5 , power dissipated by the coil is ___ watts.
50 c. 5
80 d. 20
For a 4-pole dc generator, having a progressive simplex 2layer wave – winding with 30 conductors, the commutator pitch is ___
8 c. 10
9 d. 11
Rapid stopping of an electric motor by momentarily reversing its connections to the supply is called
jogging c. plugging
inching d. sequence operation
A certain 1Ф load takes 10 kw at 75 percent power factor. In the power contract the power factor penalty is applied only to power factors below 85 percent. What size of capacitor must be used in order to avoid the penalty? The voltage is 550 volts, 60 cycles.
92.82 µF c. 2.98 µF
9.82 µF d. 22.98 µF
An induction motor driven above synchronous speed is called ___.
induction regulator c. centrifugal switch
zero – speed switch d. limit switch
A 200 kva transformer has an impedance of 15% and the power factor of the load is 85%. The primary voltage is 6,000 volts while the copper loss is 15 kw. Find the percentage voltage regulation.
13.49% c. 8.91%
15.78% d. 23.67%
What is the speed of an induction motor of six poles if the percent slip is 2.5%?
1462 rpm c. 877 rpm
1170 rpm d. 1755 rpm
The rotor poles of an 8 – pole synchronous generator shift by 10 mechanical degrees from no –load to full – load. Calculate the torque angle between the excitation voltage E0 and the terminal voltage VФ at full – load.
10º c. 30º
20º d. 40º
This is a device projected vertically upward above structures to serve as the lighting rod.
air connector c. air terminal
lightning bowl d. air rod
A transformer is designed to carry 30 times its rated current for 1 second. The length of time that a current of 20 times the rated current can be allowed to flow is
0.67 sec. c. 1.5 sec
2 sec d. 2.25 sec.
What is the normal secondary circuit current of a current transformer?
15 A c. 5 A
20 A d. 10 A
A parallel circuit has branch resistance of R1 =20 , R2 =10 , R3 =5 . If the current passing through R1 =20 resistor is 1 ampere, what is the current passing through the 10 resistor?
5 A c. 3 A
2 A d. 4 A
In a stranded conductor, what do you call the strand at the center of the conductor?
king wire c. steel wire
center wire d. center
The total power consumed by a balanced 3Ф load is 3,000 watts at 80% power factor. Two wattmeters WA and WB are connected to the line. What is the reading of WA?
2,150 watts c. 1,500 watts
2,000 watts d. 2,500 watts
A circuit with a resistance of 10 is supplied with 120 V 60 hz source. What is the phase angle between the voltage and the current?
45º c. 30º
15º d. 0º
What is the synchronous speed in rpm of a 6 - pole 60 cycle induction motor?
1,200 c. 3,600
1,800 d. 900
A 3 phase 4 wire system has the following unbalanced loads: Z1= (10+j5) , Z2= (8+j4) and Z3= (20+j0) . The line to neutral voltage of the system is 120 volts. What is the reading of the wattmeter in watts in Z3?
900 c. 1,000
720 d. 1,050
What electrode in a junction transistor corresponds to the cathode in vacuum tube?
base c. drain
emitter d. collector
An AC circuit with two resistances, which is correct?
a 1,000 ohm resistance in series to 500 ohm has a total of 6,000 ohms.
Two 1,000 ohm resistances in series has a total of 1,500 ohms.
Two 1,000 ohm resistances in series has a total of 707 ohms
Two 1,000 ohm resistances in series has a total of 2,000 ohms.
Which does not belong?
lines per square centimeter
maxwells per square centimeter
flux
gauss
The diameter of a conductor is 0.064 inch. What is the area in circular mils?
5,000 c. 3,217
10,000 d. 4,096
In a shunt motor, what is the relative connection of the armature winding with respect to the field winding?
series c. series – parallel
parallel – series d. parallel
A single – phase 2,400 volt synchronous generator draws 450 amperes at unity power factor. The synchronous impedance of the generator is (0.08 + j2.8) . What is the regulation in percent?
14.2 c. 20.1
16.3 d. 18.4
A pure semiconductor without doping is called
contaminated c. doped
extrinsic d. intrinsic
A series RLC circuit has R = 10 , L = 40 x 10-6 H and C = 60 x 10-12 F. What is the resonant frequency of the circuit in MHZ?
20.17 c. 4.49
3.24 d. 1.62
On full – load a 500 volt series motor takes 100 amperes and runs at 840 rev/min. The armature resistance is 0.1 ohm and field resistance is 0.04 ohm. Find the speed when developing half of full – load torque but with a 0.08 ohm diverter in parallel with the field winding. Assume flux is proportional to the field current.
640 rpm c. 1,464 rpm
1,020 rpm d. 1,360 rpm
A capacitor charged with 10,000 µC. If the energy stored is 1 joule, find the capacitance.
500 µF c. 5,000 µF
5 µF d. 50 µF
A 440 volt synchronous motor is taking 50 amperes at a p.f. of 0.9 lagging. The effective resistance of armature is 0.8 ohm. If the iron and friction losses amount to 600 watts, find the horse power output.
25.7 c. 23.1
37.1 d. 40.5
Three 100 µF capacitors are connected in delta to a 500 volt, three phase, 50 Hz supply. Find the line current.
15.71 A c. 31.83 A
27.21 A d. 8.66 A
A pair of copper mains. Each of 3.87 square centimeters cross section is used to transmit power a distance of 915 meters. For 10 hours a day, 80 kW at 200 volts are taken from the mains. Find the energy lost in the cables per day. Take ρ = 1.7 micro ohm – cm.
64 kW-hr c. 256 kW-hr
128 kW-hr d. 32 kW-hr
An SCR combines the features of
a rectifier and resistance
a rectifier and capacitor
a rectifier and transistor
a rectifier and inductor
A 0.09 microfarad capacitor is charged to 220 volts. How long in milliseconds will it discharged to a level of 110 volts if the discharged resistor has a resistance of 20,000 ohms?
1.5 c. 1.25
2.5 d. 0.5
The total generating capacity of a power plant is 1,600 kva. The total connected load is 2,500 kva. Average load is 1,145 kva. The maximum power demand is 1,150 kva. What is the plant factor?
46% c. 71.88%
99.5% d. 71.56%
Assuming the most efficient technologies for the extraction of energy, the fuel with the largest known reserves is
coal c. natural gas
oil d. nuclear
A three – phase 60 hz line has flat horizontal spacing. The conductors have an outside diameter of 3.28 cm with 12 m between conductors. Determine the capacitive reactance of the line to neutral if its length is 125 miles.
1.62 x 103 c. 25.3 x 106
202.4 x 103 d. 16.2 x 103
Name of the transformer that provides an almost continuously variable step-less output voltage from zero to rated line voltage.
booster c. AVR
UPS d. Variac
A circuit has a resistance of 20 and a reactance of 30 .
What is the p.f. of the circuit?
0 c. 0.832
0.55 d. 0.99
A parallel branch circuit composed of a 100 ohm resistance, 150 ohm capacitive reactance and 90 ohm inductive reactance. What is the total impedance of the circuit?
125 c. 91
100 d. 97
The most common type of the conductor used for overhead transmission lines consisting of electrical grade aluminum conductor overlaying strands of high carbon galvanized steel is called:
ACAR c. COMPACT STAND AL
ACSR d. AAC
The 65 percent taps on a compensator are used in connection with a 10 hp 220 volt three phase motor. Rated motor current is 26.4 amp, and blocked – rotor current at 220 volts is 150 amp. Calculate the percent motor current in terms of rated amperes.
369 c. 240
65 d. 568
A single – phase transformer is rated 110/440 V, 2.5 kVA. Leakage reactance measured from the low – tension side is 0.06 . Determine leakage reactance in per unit.
0.0484 c. 0.484
0.0248 d. 0.0124
Three capacitors of 50 µF, 30 µF, and 10 µF are connected in parallel. What is the total capacitance in microfarad?
15 µF c. 100 µF
90 µF d. 115 µF
What is the process of heating electrically non metallic materials such as plumber plastics, etc.?
resistive c. dielectric
capacitive d. induction
If a fault occurs near a generating station, how long does the transient component of the fault last?
10 to 15 sec c. 3 to 5 sec
5 to 10 sec d. 1 to 3 sec
A three – phase 60 Hz, 30 mile transmission line delivers
20,000 kW at 69,000 volts and 75% power factor lagging. The resistance of the line is 0.3 ohm per mile and the reactance is 0.7 ohm per mile. What is the transmission line efficiency?
93 c. 95
94 d. 96
How are multiple stop push buttons connected in a control circuit?
combination series – parallel
parallel
gang
series
A road is illuminated by two 500 candela lamps placed 6.1 meters above the center line of the road and 18.3 meters apart. Find the illumination produced on the surface of the road at a point on the center line midway between lamps.
2.29 lux c. 9.16 lux
4.58 lux d. 18.32 lux
A heater contains 1.6 kg of water at 20ºC. It takes 12 minutes to raise the temperature to 100ºC. Assume the losses due to radiation and heating the kettle to be 10 kcal. Find the power rating of the heater in kW.
0.74 c. 0.84
0.7 d. 0.8
Shunts are generally made of what material?
constantan c. aluminum
silver d. manganin
A magnetizing force of 1,000 At/m will produce a flux density of ____ in air.
1.257 mWb/m2 c. 1.257 Wb/m2
0.63 Wb/m2 d. 0.63 mWb/m2
The potential difference of a battery is 10 volts when the current is 1.5 amperes and 8 volts when the current is 2.5 amperes. Find the internal resistance of the battery.
1 c. 3
2 d. 4
A four pole, lap wound armature when driven at 600 rpm generates 120 V. If the flux per pole is 25 mWb, find the number of armature conductors.
120 c. 480
240 d. 720
A coil of 1,000 turns is uniformly wound on ring of non – magnetic material, the mean diameter being 0.2 meter. The cross –sectional area of the coil is 4 cm2, with a current of 2 amperes flowing, find the total flux in µWb.
3.2 c. 1.6
6.4 d. 4.8
What are the three colors which when mixed equally together will produce white and the combination of any two will produce different colors and intensities?
red, blue, green c. black, red, pink
yellow, magenta, cyan d. red, blue, yellow
A 500 kV line is categorized as
high voltage c. extra high voltage
ultra high voltage d. medium voltage
A circuit having a resistance of 20 and an inductance of 0.5 H is connected suddenly across a 220 V supply. Find the rate of increase of current at the instant of closing the switch.
440 A/s c. 120 A/s
220 A/s d. 480 A/s
A 350 kW, 2,300 V, three – phase resistive load is measured with two small wattmeters. Two 100/5 A current transformers and two 2,300/115 V potential transformers make this possible. Calculate the reading on each wattmeter.
874 W & 874 W c. 1,311 W & 1,311 W
218 W &218 W d. 437 W & 437 W
The transformer is rated at 550/220 V. With the low –voltage winding shorted, it requires 25 V across the 550 V winding to permit rated current through both windings of the transformer. Calculate the percent impedance.
4.55% c. 3.55%
5.55% d. 6.55%
A group of 10 luminaries, each with two 40 watt, cool – white fluorescent lamps, are installed in a classroom. An appropriate CU of 0.65 is selected from the manufacturer s chart, which also suggests an MF of 0.85. Determine the total lumens output of the luminaries.
58,000 c. 32,100
26,000 d. 64,200
A central station has annual factors as follows:
Load = 58.5% Capacity = 40.9% Use = 45.2%
The reserve carried over and above the peak load is 8,900kw.
What is the installed capacity?
20,700 kW c. 25,900 kW
29,600 kW d. 40,000 kW
A 12 µF capacitor charged at 500 volts and a 6 µF capacitor charged at 250 volts are connected in parallel. What is the potential difference of the combination?
750 V c. 375 V
500 V d. 417 V
An antenna that transmits or receives equally well in all directions is said to be __________
omni directional c. unidirectional
bi-directional d. quasi-directional
A 30 mile transmission line is to deliver 20,000 kW at 69 kV at 85% power factor. The line resistance is 0.324 ohm per mile and inductive reactance is 0.737 ohm per mile. What is the line loss?
1,050 kW c. 997 kW
376.7 kW d. 1,130.3 kW
Prior to starting of fluorescent lamp, heating of electrode is done by
starter c. filament
ballast d. heater
A frequency of 27 MHz has a wavelength of approximately______.
11 m c. 27 m
30 m d. 81 m
A type of communication that uses light rather than electricity to communicate is called_____.
laser carrier c. powerline carrier
microwave d. fiber optic
A copper wire has a diameter of 0.032 inch. What is the area in circular mils?
1,288 c. 810
1,024 d. 1,624
It is required to increase the power factor of a 750 kW three – phase balanced load from 70% lagging to 90% lagging. The line voltage is 6,900 volts, 60 hz. Specify the capacitor required to increase the power factor of this wye – connected load in microfarad per phase.
20.45 c. 18.58
22.39 d. 17.22
A signal occupies the spectrum space from 1.115 to 1.122 GHz. The bandwidth is____.
0.007 MHz c. 237 MHz
700 MHz d. 7 MHz
Two condensers of 3 and 5 µF respectively are connected in parallel. The combination is charged with 0.0056 coulomb.
What is the charge in the 3 µF condenser in coulombs?
0.01 c. 0.0021
0.005 d. 0.0035
A series circuit with 10 ohm resistor and 50 µF capacitor is suddenly connected to a dc source of 120 volts. What is the current at one time constant?
12 A c. 7.6 A
2.44 A d. 4.4 A
A room with dimensions of 72 ft x 36 ft x 13 ft requires 50 footcandles, maintenance factor of 0.7 coefficient of utilization of 0.46 and Rl of 4. Calculate the required lumens output of the lamps.
144,000 c. 402,485
136,800 d. 74,690
Instrument transformers are used in indicating and metering and with protective devices, they are used for ______
measuring c. relaying
detecting d. sensing
Reactances are connected in series: Xc1=100, Xc2=40, XL1=30, XL2=70. What is the net reactance?
80Xc c. 60XL
40Xc d. 50XL
A tuned circuit is resonant at 4 MHz. Its Q is 100. What is its bandwidth?
4 kHz c. 400 Hz
400 kHz d. 40 kHz
What is the value of Rx in kohms to be connected in parallel to a 75 kohms to reduce the value of total resistance to 10 kohms?
11.7 c. 7.5
15.7 d. 12.7
What is the burning hours that should be used in the design consideration of incandescent bulb?
1,500 c. 850
1,800 d. 650
Three capacitors of 3, 4 and 5 microfarads are connected in series with a 6 volt battery. When the current stops, what is the voltage across the 3 microfarad capacitor?
1.62 V c. 2.55 V
1.91 V d. 1.53 V
A transformer rated 2,000 kVA, 34,500/240 volts has 5.75% impedance. What is the per unit impedance?
0.0636 c. 0.0575
0.0656 d. 34.2
It refers to a device that merely boosts a signal and passes it on.
amplifier c. op – amp
booster d. repeater
What do you call an impedance that when a line to ground fault occurs, produces fault currents that are equal and in – phase?
positive sequence c. negative sequence
third sequence d. zero sequence
If 14,000 maxwells emanate from a pole, what must be its area to have a flux density of 7,000 gauss?
3 cm2 c. 2 cm2
4 cm2 d. 1 cm2
In a series or parallel LC circuit, the resonant frequency is attained when
Xc is 1/10 of XL c. Power factor angle is 90°
XL is 1/10 of XC d. Xc = XL
A light source has an illumination of 100 footcandles (fc), what is the illumination in lux?
1,204 c. 1,496
1,075 d. 1,360
What is the equivalent of the collector terminal of transistor in a FET?
grid c. source
gate d. drain
What is the percent slip of the synchronous motor when running?
3 c. 1
2.5 d. 0
If you tuned in a FM radio station ranging from 88 MHz to 108 MHz, what is the maximum capacitance in picofarads if L = 0.1 microhenry?
34.5 c. 32.7
38.6 d. 36.8
In an induction motor, what is the percent slip if the speed is 3,510?
1 c. 2
1.5 d. 2.5
What is the unit of electrical resistance?
volt c. ohm
ampere d. watt
Three equal resistors are connected in series. The voltage in one of the resistors is 15 volts. What is the applied voltage?
30 V c. 40 V
45 V d. 50 V
An ideal full wave rectifier with non inductive load has zero transformation losses. What is the efficiency?
100 c. 80
90 d. 70
A 750 Hp, 2,400 volts three –phase motor has a power factor 90% and efficiency of 95% is to be operated to a 13.2 kV utility service thru a wye – delta connected transformer. What is the total kVA of the transformer bank?
575 c. 595
654 d. 615
What category do 115 kV – 230 kV belong?
low voltage c. high voltage
medium voltage d. extra high voltage
What is the device that converts DC power to AC?
converter c. SCR
inverter d. Rectifier
A voltmeter has a resistance of 80 ohms per volt deflection. What current will flow in milliamperes (mA) when connected across 150 volt source if it has a 200 volt scale deflection?
11.5 c. 9.4
10.5 d. 12
The power drawn by a balanced 3Φ load is 3,000 watts at 80% power factor. If two wattmeters WA and WC are used, what is the reading of WC?
800 c. 900
950 d. 850
What is the most common cause of failure in cable termination and splicing? a. tracking
poor shielding
wrong clearance
improper insulation penciling
In a series RLC circuit, the resistance is 200 Ω, the inductance is 10 mH, and the capacitance is 4 µF. If the circuit is connected across 100 volt source, what is the current?
0.144 c. 0.12
0.15 d. 0.13
A 3,600 V 500 kVA 60 Hz 3 phase Y – connected generator on test yields the following results: Mechanical and iron losses is 10 kW; field current at full – load 100% p.f. is 50 A; field current at full – load 80% p.f. is 70 A; resistance per phase of armature winding is 0.4 ohm. The exciter voltage is constant at 120 volts and voltage control is done by means of rheostat.
Determine the full – load armature current at 80% lagging p.f.
95.6 A c. 64.2 A
99.8 A d. 80.2 A
Three of the following terms in magnetic induction are identical. Which is distinct among the following?
maxwells c. flux
lines d. gauss
One kW-hr is equal to
3,600 watts c. 860 k calories
1,000 watts d. 4,186 newtons
A power plant is driven by a turbine at a rate of 10 cubic meters per second and with a head of 235 meters. If the plant efficiency is 0.65, calculate the power plant output.
10,000 kW c. 35,000 kW
15,000 kW d. 25,000 kW
At a certain point in a 69 kV transmission line, the positive sequence impedance is j0.15 p.u., and the zero – sequence impedance is j0.55 p.u. Calculate the fault current if a line – to – line fault occurs. The base is 50 MVA.
3,511 amperes c. 420 amperes
1,890 amperes d. 2,414 amperes
A 3Φ, 220 volt, 10hp induction motor having a power factor of 0.8 has 3% losses. Determine the current drawn by the motor.
25.23 amps c. 20.18 amps
43.69 amps d. 14.56 amps
The three phase unbalanced currents are:
Ia = 10 cis (-30°)
Ib = 0
Ic = 10 cis (150°)
Find the negative sequence current of phase a.
8.66 cis 30 c. -5.77
5.77 cis (-60) d. 5.77
A test is performed on a 230 volts, delta connected synchronous motor having 92% efficiency and 85% power factor. With 6 volts dc impressed across its terminals, the current reading is 90 amperes. Determine the ohmic resistance per phase.
0.067 Ω c. 0.1 Ω
0.044 Ω d. 0.15 Ω
A 20 Hp, 110 V dc shunt motor has an efficiency of 88% and an exciting current of 4 amperes and an armature resistance of 0.04 ohm. What starting resistance is required for full load torque?
0.98 Ω c. 0.95 Ω
0.94 Ω d. 0.69 Ω
A 100 km transmission line has a 1,200 ohms shunt reactance. What is the per km shunt reactance?
1,200 Ω c. 12 Ω
120,000 Ω d. 120 Ω
What is the total energy generated by a station in kWHr in a year if its maximum demand and annual load factor is 150 kW and 45% respectively?
591,300 c. 24,637
1,314,000 d. 67,500
When luminaries direct 90 to 100% of their output downward is considered a ______.
direct lighting c. indirect lighting
local lighting d. luminaries
A three phase squirrel cage motor is started by a wye – delta starter. What shall be its starting torque relative to its rated voltage starting torque?
33.3% c. 57.7%
42.3% d. 100%
It took a heater of 2 kW, 158 minutes to raise by 30°C the temperature of water in an insulated vessel. How many gallons of water are inside the vessel?
30 gallons c. 40 gallons
10 gallons d. 20 gallons
A certain shunt motor armature has a resistance of 0.07 Ω and current of 50 amperes at 120 volts. Determine counter emf.
108.5 V c. 112.2 V
116.5 V d. 118.3 V
The kH of kWHr meter is 3.2. The disc takes 32 seconds to complete one (1) revolution. What is the load rating?
0 c. 360 watts
800 watts d. 2.1 watts
In a balanced 3Φ system the phase a voltage is 132.8 cis 0°, what is the line to line Vca voltage?
230 cis 30° c. 230 cis (-60°)
230 cis (-30°) d. 132.8 cis 120°
The instantaneous value of the voltage is given by its equation v = 105 sin ωt – 25 sin 3ωt + 15sin (6ωt- 30°).
What is its rms value?
77 volts c. 105 volts
190 volts d. 205 volts
A dc shunt motor develops 15 Hp at 120 V. If the effective armature resistance is 0.061 ohm and the field winding draws 2 amperes, what is the overall efficiency?
90% c. 95%
93% d. 94%
V12 = 100 cis 30° and V23 = 50 cis 120°. Evaluate V12 - V23.
62 cis 6.2° c. 111.8 cis 3.4°
127.3 cis 40° d. 62 cis (-6.2)°
A 200 microfarad capacitor is connected in series with a 10 Ω resistor. The circuit is connected to a 24 V battery. What is the initial current when putting the switch on?
1.2 A c. 0.255 A
2.4 A d. 0.0125 A
The percent impedance of a line is 6% at 34.5 kV and 100 MVA base. What is the ohmic impedance?
2.32 c. 0.72
3 d. 1.2
The rms value of sinusoidal ac current is equal to its value at an angle of ___ degree.
60 c. 30
45 d. 90
Transformer are rated in kVA instead of kW because
load power factor is often not known
kva is fixed whereas kw depends on load
total transformer loss depends on volt – ampere
it has become customary
A synchronous motor having 40% reactance and a negligible resistance is to be operated at rated load unity p.f. If the motor is rated 100 volts and 100 A, what is the value of induced emf? Assume delta connected motor.
180 V c. 4001 V
70 V d. 108 V
The starting winding of a single – phase motor is placed in the
rotor c. armature
stator d. field
What is the current per phase in the primary windings of a 3 phase /Y connected 6,600/400 V, 500 kVA, 50 Hz transformer. Neglect no – load current.
43.74 A c. 14.58 A
75.76 A d. 25.25 A
A 3 Hp 208 volt three phase motor is started by the Y - method. If the starting current is 54 amp when rated voltage is applied, what current will flow when the Y - switch is used?
93.5 A c. 31.2 A
162 A d. 18 A
An 80:5 current transformer is connected to a 5 amp ammeter. If the latter registers 3.65 amp, what is the line current?
58.4 A c. 21.9 A
80 A d. 3.65 A
It is desired to purchase a synchronous condenser to correct the 2,400 kVA 0.67 lagging p.f. load in an industrial plant to 0.95 lagging. Neglecting losses, calculate the kVA input rating of the required synchronous condenser.
2,280 kVA c. 1,500 kVA
1,608 kVA d. 1,250 kVA
The armature of a 230 volt shunt motor has a resistance of 0.18 ohm. If the armature current is not to exceed 76 amp, calculate the resistance that must be inserted in series with the armature at the instant of starting. Assume a 2 volt drop at the brushes.
2.82 Ω c. 3.18 Ω
3 Ω d. 2.69 Ω
It is desired to step down the three phase voltage from 6,600 to 460 volts using Y - transformer connection. What should be the ratio of transformation of each transformer?
1:8.3 c. 1:14.3
14.3:1 d. 8.3:1
In a laboratory experiment, the impedance of a coil was obtained at 60 Hz and 30 Hz. These are 75.48 ohms and 57.44 ohms, respectively. What is the inductance of the coil?
150 mH c. 42.5 mH
182.5 mH d. 2.1 mH
A power customer is applying for source and listed the following loads:
5 – 15 Hp motors
3 – 5 Hp motors
Lighting loads – 8 kW
Miscellaneous loads 3 – 5 kW
The demand factor is 65%, load factor is 46% and the power factor is 80%. What is the maximum kW demand of the customer?
78 c. 69
64 d. 57
A 250km transmission line has the following parameters: resistance per km 0.05 ohm, capacitive reactance per km 625,000 ohms and inductive reactance per km 0.2 ohm. What is the series impedance?
(37.5 + j150) Ω c. (12.5 + j50) Ω
(12.5 – j2,450) Ω d. (75.5 – j2,450) Ω
Combination of switch and fuse.
relay c. fuse cut – out
circuit breaker d. safety switch
The phase b voltage and the phase b current of a balanced 3 phase system are: V = 220 sin (ωt + 210°) and I = 10 sin (ωt - 180°). What is the power of the system?
3,300 W c. 1,905 W
5,716 W d. 3,810 W
Three similar coils, when connected in delta to a 3 phase, three wire, 400 volt, 50 Hz supply, take a line current of 7 A at a p.f. of 0.8 lagging. If the coils are now connected in star to the same supply, calculate the line current and total power. a. 2.33 A, 3,879 W c. 7 A, 1,293 W
b. 7 A, 3,879 W d. 2.33 A, 1,293 W
Calculate the error in the ammeter which reads 3.25 A in a circuit having a series standard resistance of 0.01 Ω, the potential difference measured across this standard resistance being 0.035 V.
7.7% c. 6.7%
7.1% d. 5.1%
Estimate the distance over which a load of 15,000 kW at 0.85 p.f. can be delivered by a three – phase transmission line having conductors of steel – cored aluminum each of resistance 0.56 Ω/km. The potential difference at the receiving end is to be 132 kV and the loss in transmission is not to exceed 7.5%.
122 km c. 142 km
110 km d. 150 km
An iron ring, 100 cm mean circumference, is made from an iron rod of round cross – section of 10 cm2. It is wound with 200 turns. What current would be necessary to produce a flux of 1 mWb. Relative permeability of iron = 500.
976 A c. 796 A
697 A d. 769 A
The force between two wires carrying currents in opposite directions is 20.4 kg/m when they are placed with their axes 5 cm apart. Calculate the current in one conductor when current flowing through the other conductor is 5,000 A.
1,000 A c. 1,500 A
10,000 A d. 5,000 A
Two positive point charges 12 x 10-10 coulomb and 8 x 10-10 coulomb are placed 10 cm apart. Find the work done in bringing the two charges 4 cm closer.
57.6 x 10-8 J c. 144 x 10-8 J
14.4 x 10-8 J d. 5.76 x 10-8 J
What is the resonant frequency of a circuit when L is 50 microhenrys and C is 40 picofarads are in parallel?
7.96 MHz c. 3.56 MHz
79.6 MHz d. 1.78 MHz
Which relay is used for feeders?
MHO relay c. Merz price protection
Translay relay d. Buchholz relay
A two branch parallel circuit with one branch of R = 50 ohms and a single unknown element in the other branch has the following applied voltage and the total current:
v = 100 cos(1500t + 45°) volts
it = 12 sin (1500t + 135°) amperes
Find the unknown element.
R = 8.33 Ω c. L = 10 H
R = 10 Ω d. L = 8.33 H
The following information is given for two transformers connected in parallel and delivering a total load of 300 kVA:
Transformer1
Transformer2
Rating = 150kVA
Rating = 250kVA
6,900/230 volts
6,900/230 volts
Ze – p1 = 9.4 Ω
Ze – p2 = 5.8 Ω
Calculate the load current supplied by each transformer. a. 26.9 A, 16.6 A c. 734 A, 1190 A
b. 21.7 A, 36.2 A d. 24.5 A, 39.7 A
A 3 phase, 11 kV transmission line 10km long delivers 200 kW load at 0.8 lagging power factor. The resistance of the line is 0.9 Ω per km per phase. What is the percentage power loss in the line assuming 11 kV voltage at the receiving end.
1.27% c. 4.27%
3.27% d. 2.27%
Fusion energy is produced when
chemical compounds combined
fuel burns
nuclear particles divides
nuclear particles combined
Given Y – connected impedances Za = (2 + j2) Ω, Zb = (5 – j10) Ω, and Zc = (5 + j10) Ω. Find the equivalent delta impedance Zbc.
(41.22 + j31.23) Ω c. (30 – j10) Ω
(41.22 – j31.23) Ω d. (-10 + j30) Ω
One watt – second is also equal to which one?
980 dynes – cm c. 1 erg – second
1 joule d. 3 gram – calorie
A 115 kV line has a horizontal configuration. The distance between adjacent conductors is 9 ft. What is the geometric mean distance of the line?
9 ft c. 11.34 ft
12 ft d. 18 ft
The total capacitance of two capacitors is 0.03 µF when joined in series and 0.16 µF when connected in parallel. Find the capacitance of each capacitor.
0.12 µF, 0.04 µF c. 0.03 µF, 0.08 µF
0.24 µF, 0.08 µF d. 0.06 µF, 0.16 µF
A hydroelectric plant generates 100 MW at an available head of 200 m and an overall efficiency of 75%. What quantity of water in cubic per second is required?
1,200 c. 26
122 d. 68
The illumination of a room is being designed. The illumination intensity required is 50 footcandles. The maintenance factor is 70% and coefficient of utilization is 60%. If the room is 20 ft by 15 ft, what is the total required lumens output of the lamp?
35,000 lumens c. 6,300 lumens
10,500 lumens d. 12,800 lumens
One kW is equal to ___ ft-lb/sec.
1,356 c. 1,055
738 d. 550
A battery produces a current of 0.6 A when the external resistance is 2 Ω and 0.2 A when the external resistance is 12 Ω. Find the emf of the battery.
3 V c. 9 V
6 V d. 12 V
An open delta bank delivers a balanced three – phase load of 60 kVA at 460 volts. What current flows in the secondary of each transformer?
65.2 A c. 150.6 A
130.4 A d. 75.3 A
The flux density emanating from a pole of a generator is 20,000 gauss. A conductor one meter long cuts the flux perpendicularly at a speed of 40 m per second. What voltage is developed?
800 volts c. 230 volts
80 volts d. 8 volts
The capacitive reactance of a 40 km 34.5 kV line is 90,000 ohms per km. What is the total capacitive reactance of the line?
2,250 ohms c. 6,750 ohms
1.08 x 107 ohms d. 3.6 x 106 ohms
Two voltage generators are in series. The voltages being generated are Vab = 50 sin (ωt - 30°) and Vbc = 100 sin (ωt + 60°). What is the output voltage Vac?
111.83 cis 33.5° c. 145.5 cis 50.1°
50 cis 30° d. 150 cis 30°
A lead – acid battery having a 100 A capacity is 25% charged. After being charged at 10A for 5 hours, it will be approximately ___ charged.
1/2 c. fully
3/4 d. over
A current of 1 ampere passes through a relay coil of 500 turns. What is the mmf?
628 gilberts c. 9,425 gilberts
943 gilberts d. 595 gilberts
The illumination of a room is being designed from the following data:
Room length = 40 ft. Required foot – candle = 200
Room width = 24 ft Lumens per lamp = 3,300
Coefficient of utilization = 0.60 No. of rows = 5
Maintenance factor = 0.70
What is the number of lamps per row?
40 c. 28
35 d. 140
What is the tesla a unit of?
permittivity c. permeance
capacitance d. magnetic induction
A coil having and inductance of 0.05 H and resistance of 10 ohms is connected in series with a 25 µF capacitor across a 220 V ac source. What is the resonance frequency of the circuit?
77.2 Hz c. 60 Hz
135.2 Hz d. 142.4 Hz
Two – wattmeter method is applied to a 3 phase motor running at full – load. Two wattmeters indicate 85.5 kW and 34.7 kW, respectively. What is the operating power factor of the motor?
87.45% c. 80.69%
89.49% d. 94.76%
A transmission line consists of two solid aluminum conductors having a radius of 2.5 cm and separated on centers by a distance of 3.6 m. Find the total line inductance in millihenrys per meter.
2.09 x 10-3 c. 0.0209
1.044 x 10-3 d. 0.0104
If output power of a radio receiver is doubled, its volume is increased by _____ db.
2 c. 1
3 d. -3
Which of the following methods is used to start a synchronous motor?
resistance starter in the armature circuit
damper winding
star – delta starter
damper winding in conjunction with star – delta starter
The power factor of an alternator is determined by its ______.
speed c. excitation
load d. prime mover
A three – phase induction motor has a nameplate speed of 1,720 rpm. What is the rotor frequency?
4.44 Hz c. 1.8 Hz
2.7 Hz d. 5 Hz
A 40 microfarad capacitor is connected in parallel with 40 ohm resistor. What power is drawn when source voltage is V = 220 sin ωt volts?
1825 watts c. 1210 watts
1010 watts d. 1620 watts
The percentage overloading of two 20 kVA transformers when supplying a balanced 3 – phase load of 40 kVA in a V – V bank is ___ percent.
15.5 c. 73.2
57.7 d. 33.3
A 3 phase, 3 wire feeder supplies an industrial plant with the following data:
Line voltages: Vab = 230 0 V, Vbc = 230 240 V
Line currents: Ia = 110 -36.87 A, Ic =125 53.13 A
What is the average power factor of the plant?
0.89 lagging c. 0.93 leading
0.89 leading d. 0.93 lagging
A 3 phase, 3 wire transmission line has an impedance per wire of (3 + j7) ohms, the receiving end load is 1,950 kW, 0.65 power factor lagging with line to line voltage of 13,200 volts. Determine the kVAR of the capacitor to be connected at the receiving end to make the p.f. at that end equal to 0.8 lagging at 13,200 volts.
1,482 c. 817
2,280 d. 1,464
Two 100 watt, 200 volt lamps are connected in series across a 200 volt supply. The total power consumed by each lamp will be ___ watts.
25 c. 100
50 d. 200
A conductor cuts 1 weber of flux per sec. The average voltage generated in the conductor is _____.
108 mV c. 100 mV
1000 mV d. 10 V
A 0 – 1 mA meter has a sensitivity of
1mA c. 1 k
1 k /volt d. 1000 A
For a dc series motor with saturated condition of the field circuit, the torque developed is proportional to
speed c. Ia2
V12 d. Ia
A 100 µF capacitor in series w/ a 50 ohm resistance is connected suddenly across a 125 volt dc supply. What is the voltage in the capacitor after 5 msec.?
125 V c. 56.4 V
120 V d. 79 V
The gas inside the inner discharge tube of a sodium vapor lamp is
argon c. nitrogen
neon d. helium
The maximum efficiency of a 100 kVA transformer having iron loss of 900 watts and full – load copper loss of 1600 watts occurs at ___ kVA.
56.3 c. 75
133.3 d. 177.7
In a 4 - pole, 35 slot, dc armature, 180 electrical degree coil span will be obtained when coils occupy ___ slots.
1 and 10 c. 2 and 11
1 and 9 d. 3 and 13
The transients w/c are produced due to sudden but energetic changes from one steady state of a circuit to another are called ____ transients.
initiation c. transition
relaxation d. subsidence
A 13.8 kV/440 V, 50 kVA single phase transformer has a leakage reactance of 300 ohms referred to the 13.8 kV side. Determine the per unit value of the leakage reactance for the low – voltage base.
0.305 c. 0.097
0.0305 d. 0.079
While describing the sheath of a cable, the abbreviation XLPE means ______ polyethylene.
cross – layer c. cross – linked
external – layer d. extra – long
Two capacitors of 0.1 µF, 250 V and 0.2 µF, 500 V are connected in series. What is the maximum voltage that can be applied across the combination?
375 c. 750
250 d. 500
A dc shunt motor draws an armature current of 98.16 A at 120 V. What is the hp output of the motor if the armature effective resistance is 0.06 ?
15.8 c. 7.5
22 d. 15
A non sinusoidal emf having the equation v = 141.4 sin (ωt - 60 ) – 56.6 sin (ωt - 30 ) + 35.4 sin (5ωt - 90 ) is impressed upon a circuit. If the current has the equation I = 28.3 sin (ωt - 30 ) + 17 sin (3ωt - 90 ), calculate the power factor of the circuit.
0.857 c. 0.785
0.578 d. 0.958
A diesel power plant has an overall efficiency of 30%. If the calorific value of diesel is 18,000 BTU/1b and cost Php6.00 per liter, how much is the fuel cost of production per kwhr of energy? Take the density of diesel as 900 grams per liter.
Php1.91/kW-hr c. Php2.12/kW-hr
Php1.85/kW-hr d. Php2.45/kW-hr
Two single phase transformers operate in parallel. Transformer 1 is rated 100 kVA with 4% reactance while transformer 2 is rated 75 kVA with 3% reactance. The transformers have secondary voltages of 220 volts and same voltage ratio. If the common load is 125kva at 80% p.f. lagging, determine the kVA sharing of each transformer.
71.43 kVA & 53.57 kVA c. 62.5 kVA & 62.5 kVA
75 kVA & 50 kVA d. 82.5 kVA & 42.5 kVA
In a 13.8 kV, 10 MVA base three phase system a phase to phase fault occurs. If the thevenin s equivalent impedance of the system is 2.63%, what is the magnitude of the fault current?
13,800 A c. 27,600 A
15,900 A d. 7,970 A
The sequence components of phase a current are:
Ia = 0
Ia1 = (90 + j5.78) A
Ia2 = (10 - j5.78) A
Determine the phase C current.
91.61 131 A c. 100 120 A
100 0 A d. 91.61 251 A
The CT ratio and PT ratio used to protect a line are 240 and 2000, respectively. If the impedance of each line is 10 , what is the relay impedance to protect the line from fault?
83.33 c. 48,000
1.2 d. 12
What is the most probable per unit transient reactance for an alternator rated 100 MW?
0.02 c. 1.0
0.30 d. 0.1
What should be the kV rating of a surge arrester to be used for an 11 kV ungrounded system?
18 kV c. 12 kV
16 kV d. 9 kV
A three – phase, 4 – pole induction motor with open – circuited rotor is connected to a 400 V, 50 Hz, three – phase supply. The motor will run at ____ rpm.
1500 c. 1450
1480 d. 0
What is the self geometric mean distance of a 3 – strand bundle made of ACSR Rail conductors with 45 cm between conductors? The GMR of ACSR Rail is 0.0386 ft.
0.4832 ft c. 0.3842 ft
0.2834 ft d. 0.4382 ft
A 3 phase balanced system working at 0.9 p.f. lagging has a line loss of 3,600 kW. If p.f. is reduced to 0.6, the line loss would become _____ kW.
8,100 c. 5,400
1,600 d. 4,800
A 55,000 kW thermal power plant of NPC delivers an annual output of 283,000 MWHr with a peak load of 44 MW. The annual load factor of the plant is nearest to
0.75 c. 0.76
0.72 d. 0.73
For power transformers, the conservator tank is intended to minimize
heating c. oil slugging
internal pressure d. breathing
A generator rated 15 MVA, 13.2 kV has 8% impedance is connected to a step – up transformer of 20 MVA, 13.8/230 kV for transmission. What is the new per unit impedance using transformer ratings as base value?
0.146 c. 0.098
0.102 d. 0.107
In a vacuum tube, what is the ratio of a small change in plate voltage to a small change in grid voltage?
amplification ratio c. current ratio
voltage ratio d. amplification factor
What is the normal indication on a megger when checking insulation?
one c. middle of scale
infinity d. zero
A flux of 1,500,000 maxwells links a coil having 350 turns. This flux through the coil is decreased to zero at a uniform rate in 0.2 sec. Determine induced emf during this time interval.
1 volt c. 26.25 volts
857 volts d. 8.57 volts
What electric power is required to drive a pump which must raise water 96ft and supply 2,600 gpm? One gallon water weighs 8.3lbs. motor and pump efficiency are 90% and 70%, respectively.
46.8 kW c. 29.5 kW
74.3 kW d. 60.2 kW
The winding of a 4 – pole alternator having 36 slots is short by 2 slots. What is the pitch factor?
0.9397 c. 0.9566
0.9725 d. 1.0
The unit of magnetic field intensity in the CGS system is
gauss c. ampere – turn per meter
gilbert d. Oersted
What is the work done in moving a 50 C electric charge through a distance of 50cm in the direction of a uniform electric field of 50 kV/m?
2.5 joules c. 1.25 joules
500 joules d. 125 joules
A coil with L = 2 H and R = 362 is connected to a 230 V, 50 Hz supply. Calculate the energy stored when the instantaneous voltage is zero.
0.317 J c. 0.151 J
0.051 J d. 0
A system is consists of three equal resistors connected in delta and is fed from a balanced three –phase supply. By how much power is reduced if one of the resistors is disconnected?
33% c. 50%
67% d. 25%
A round wire has 250,000 CM. Find its diameter in inches.
1/2 c. 0.16
1/4 d. 0.08
One horsepower is equal to _____.
33,000 ft –lb c. 746 watt –sec
550 ft –lb/sec. d. 252 cal
Which of the following is the most probable impedance of a 100 MW alternator?
5% c. 10%
100% d. 20%
At a 34.5 kV substation, the available fault current is 10 p.u.
What is the available fault MVA if the base MVA is 50?
50 c. 200
100 d. 500
A solenoid has a magnetic reluctance of 2.2 x 10-3. It has 300 turns. What is the total flux when the current flowing is 0.5 ampere?
9.52 x 104 c. 8.57 x 104
9.82 x 104 d. 9.12 x 104
The instantaneous value of the voltage is given by the equation e = 105 sin ωt – 25 sin (3ωt + 60°) + 15 sin (6ωt + 30°). Find its rms value.
77 volts c. 190 volts
105 volts d. 205 volts
A dc shunt motor develops 15 Hp at 120 V. If the effective armature resistance is 0.061 ohm and the field winding draws 2 amperes, what is the overall efficiency?
90% c. 95%
93% d. 94%
A voltage wave is given by v = 100 sin 314t. How long does it take this waveform to complete one – fourth cycle?
20ms c. 5 ms
10 ms d. 1 ms
An ac voltage (100 + j60) volts is applied to a circuit and the current so produced is (-4 + j10) amperes. The power consumed by the circuit is
-400 W c. 200 W
100 W d. 500 W
The voltages across two series connected circuit elements are V1 = 50 sin ωt volts and V2 = 30 sin (ωt - 30°) volts. What is the rms value of the applied voltage?
54.77 V c. 56.57 V
80 V d. none of the above
A 240 V, 50 Hz series RC circuit takes an RMS current of 20 amperes. The maximum value of the current occurs 1/900 second before the maximum value of the voltage. The p.f. of the circuit is
0.92 c. 0.866
0.94 d. 0.8
A series RL circuit has the following data:
R = 10 ohms L = 0.02 H
e = 150 + 100 sin ωt + 50 sin 3 ωt volts w = 500 rad/sec
t – time, seconds
What is the average power of the circuit?
2875 watts c. 2645 watts
2350 watts d. 2512 watts
A circuit which has Wo = 106 rad/sec, C = 10 pF and Q – factor of 100, must have a resistance of ____ kohm
10 c. 1
5 d. 100
A hydroelectric plant generates 100 MW at an available head of 200 m at an overall efficiency of 75%. What quantity of water in cubic meter per second is required?
68 c. 122
1200 d. 26
A 100 liter of water is heated from 20°C to 40°C. How many kWHr of electricity is needed assuming no heat loss?
4.2 c. 5.6
2.3 d. 3.7
A generator has an output of 10 kW. What is its output in joules per sec?
10,000 c. 80,000
100,000 d. 1,000
The difference between the front pitch and the back pitch of a retrogressive lap winding is 2. If the front pitch is 21, what is the back pitch?
19 c. 21
23 d. 21.5
The transformer used to serve a customer is rated 5 MVA, 13.8 kV/480 V and its impedance is 5%. The cable connecting the breaker to the transformer has an impedance of 0.032 ohm per phase. What is the fault current if a three phase fault occurs at the breaker?
8000 A c. 6000 A
5000 A d. 1200 A
V12 = 100 cis 30° and V23 = 50 cis 120°. Evaluate V12 - V23.
62 cis 6.2° c. 111.8 cis 3.4°
127.3 cis 40° d. 62 cis (-6.2°)
A 5 mH pure inductance is connected in parallel with one µF capacitor. What frequency shall the circuit be in antiresonance?
250 Hz c. 60 Hz
2250 Hz d. 100 Hz
A 200 microfarad capacitor is connected in series with 10 Ω resistor. The circuit is connected to a 24 V battery. What is the initial current when putting the switch on?
1.2 A c. 0.225 A
2.4 A d. 0.0125 A
A 115 kV line has vertical configuration with 9 ft spacing. The diameter of the 336.4 ACSR is 0.721 inch. What is the total capacitance if the length of the line is 20 km?
0.282 µF c. 2.2 µF
0.187 µF d. 5.25 µF
In a certain circuit analysis, the bases chosen are 34.5 kV and 100 MVA. What is the base impedance?
11.9 Ω c. 23.8 Ω
7.5 Ω d. 5 Ω
The percent impedance of a line is 6% at 34.5 kV and 100 MVA base. What is the ohmic impedance?
2.32 c. 0.72
3 d. 1.2
A 69 kV/13.8 kV, 7.5 MVA transformer has 8% impedance. What is its impedance at 100 MVA base?
0.6% c. 800%
8% d. 106.7%
A 50 MW coal – fired power plant has an average heat rate of 11,000 BTU per kWHr. Coal has a heating value of 13,000 BTU per pound. The plant has a load factor of 80%. How much coal is burned per day?
8.2 x 106 lb c. 1.2 x 105 lb
7.2 x 106 lb d. 8.1 x 105 lb
A dc current of 50 amperes flows through a long straight conductor. Determine the force on a magnetic pole of 50 unit pole strength placed 5 cm from the conductor.
100 dynes c. 100 dynes
1000 dynes d. 200 dynes
The load on a three phase wye connected 220 V system consists of three 6 Ω resistances connected in wye and in parallel with three 9 Ω resistance connected in delta. The magnitude of the line current is
36.66 A c. 42.34 A
24.44 A d. 63.50 A
On a symmetrical 3Ф system, phase sequence ABC, a capacitive reactance of 8 Ω is connected across BC, and a coil R + jXL across AB. Find R and XL such that IB = 0.
4 Ω & 6.93 Ω c. 6.93 Ω & 4 Ω
69.3 Ω & 4 Ω d. 4 Ω & 69.3 Ω
Three unbalanced 3Ф line voltages are given as follows:
VA = 10 cis 30°
VB = 30 cis (-60°)
VC = 15 cis 145°
What is the negative sequence component of line voltage VC?
8.24 cis (-156.2°) c. 8.24 cis (-276.2°)
8.24 cis (-36.2°) d. 0
A 350 kW, 2,300 V, three – phase resistive load is measured with two small watt – meters. Two 100/5 A current transformers and two 2,300/115 V potential transformers makes this possible. The reading of each wattmeter in watts is
505 c. 450
437 d. 473
A 440 V, 70 Hp shunt motor has an armature of 0.185 Ω and field resistance of 350 Ω. The current drawn by this machine is 135 A at full load. If this machine is to deliver torque equal to 175 percent of that at full – load, what would be the resistance of its starter?
2 Ω c. 1.695 Ω
1.2 Ω d. 5.6 Ω
The flux density emanating from a pole of a generator is 20,000 gauss. A conductor one meter long cuts the flux perpendicularly at a speed of 40 m per second. What voltage is developed?
800 volts c. 230 volts
80 volts d. 8 volts
The resistance of the field winding of a dc machine is 0.25 Ω at 25°C. When operating at full –load, the temperature of the winding is 75°C. The temperature coefficient of resistance of copper is 0.00427/°C at 0°C. Find the resistance of the field winding at full –load.
0.298 Ω c. 0.512 Ω
0.315 Ω d. 0.271 Ω
The capacitive reactance of a 40 km 34.5 kV line is 90,000 ohms per km. What is total capacitive reactance of the line?
2250 Ω c. 6750 Ω
1.08 x 107 Ω d. 3.6 x 106 Ω
Three unbalanced 3Ф line currents are:
Ia = 10 cis (-30°)
Ib = 0
Ic = 10 cis (150°)
What is the phase b positive sequence current?
8.66 c. 5.77
5.77 cis 240° d. 8.66 cis 120°
A certain generator generates 1,500,000 joules per minute.
What is the output in kW?
50 c. 25
500 d. 125
A 3 phase bank serves four customers with the following loads:
Customer A = 80 kW at 65% p.f.
Customer B = 60 kW at 85% p.f.
Customer C = 100 kW at 90% p.f.
Customer D = 120 kW at 70% p.f.
What is the equivalent power factor?
82.16% c. 76.66%
79.21% d. 84.37%
A 5 km long, three phase 34.5 kV line has a horizontal configuration of 4 ft spacing. The conductors are 336.4 ACSR with GMR of 0.0244 ft. What is the inductance of the line?
5.33 mH c. 10.22 mH
15.12 mH d. 12.02 mH
Two voltage generators are in series. The voltages being generated are Vab = 50 sin (ωt - 30°) and Vbc = 100 sin (ωt + 60°). What is the output voltage Vac?
111.83 cis 33.5° c. 145.5 cis 50.1°
50 cis 30° d. 150 cis 30°
A short 230 kV transmission line has an impedance of 5 cis 78° ohms. The sending end power is 100 MW at 230 kV and 85% power factor. What is the line loss?
1.21 MW c. 962 kW
728 kW d. 272 kW
A 25 kVA, 550/220 V transformer has a rated copper loss of 350 watts. With the low voltage winding shorted it requires 25 V across the high voltage winding to permit rated current through both windings of the transformer. The percent reactance of the transformer is
5.72 c. 4.54
1.4 d. 4.32
A 5,000 kVA transformer has a rated copper loss of 30,118 watts. The maximum demand on the bank within the past year was 81% of the rated capacity and the loss factor was 26.75%. What was the total annual copper energy loss in the bank?
57,120 kW-Hr c. 46,300 kW-Hr
213,700 kW-Hr d. 173,000 kW-Hr
Three, 1Ф, 75 kVA transformers are banked in delta supplying a balanced three –phase load of 160 kVA at 0.8 p.f. lagging. If one transformer is removed for repair, what is the minimum amount in kVAR of capacitor bank needed to prevent the overloading of the remaining units?
86.73 c. 63.78
96 d. 73.86
A 6 pole, 50 Hz, three phase induction motor is running at 950 rpm and has a rotor copper loss of 5 kW. The rotor input in kW is
100 c. 95
105 d. 110
A synchronous motor absorbing 60 kW is connected in parallel with a load of 240 kW having a lagging p.f. of 0.8. If the combined load has a p.f. of 0.9 lagging, what is the value of the leading kVAR supplied by the motor?
145.4 c. 17.3
180 d. 34.6
A 60 Hz, three phase 100 mile transmission line draws a charging current of 0.5 A per mile when the line is tested at 100,000 V to neutral. The total capacitive susceptance of the line is nearest to
5 x 10-4 mho c. 5 x 10-6 mho
8.66x 10-4 mho d. 2.9 x 10-4 mho
A three phase, 11 kV transmission line is 10 km long and delivers 200 kW load at 0.8 lagging power factor. The resistance of the line is 0.9 ohm per km per phase. What is the percentage power loss in the line assuming 11 kV voltage at the receiving end?
2.27% c. 4.27%
3.27% d. 5.27%
A generating station has a maximum load of 20 MW for the year and the maximum loads on the substations are 7.5 MW, 6 MW, 5.5 MW and 4.5 MW. The diversity factor is
1 c. 1.175
1.5 d. 1.75
A room 8 m x 12 m is lighted by 15 lamps to fairly uniform illumination of 100 lumens per sq. meter. What is the coefficient of utilization if the output of each lamp is 1,600 lumens?
30% c. 50%
40% d. 60%
One hundred kW is equivalent to ____ joules/second.
100 c. 10,000
1,000 d. 100,000
Capacitors are said to
block AC and pass DC
block DC and pass AC
pass AC and DC
block AC and DC
When a high voltage AC circuit breaker is tested for
endurance, it is tested for at least ___
1,000 c. 10
100 d. 5
The number of cycles in which a high speed circuit breaker can complete its operation is
3 to 8 c. 20 to 30
10 to 18 d. 40 to 50
A graphical representation between discharge and time is known as ___
monograph c. hydrograph
hectograph d. topograph
One volt is equal to ___ abvolts.
106 c. 108
1,000 d. 10-2
A fully – charged lead – acid cell has an open circuit voltage of about ____ volt.
2.1 c. 2.3
2.2 d. 2.5
Which of the following is not a standard distribution voltage?
6.24 kV c. 13.8 kV
16 kV d. 11 kV
What is the total capacitance of two 20 µF capacitors in series?
40 µF c. 40 pF
10 µF d. 10 pF
The fuse used for the overhead primary distributors is
cartridge c. expulsion
dual element d. fast acting
The power required to produced a gain of 10 dB over 4 watts of original power is ___ watts.
80 c. 0.4
40 d. 8
A type of motor that overspeed at a very light load.
shunt c. flat – compound
over – compound d. series
What is the most probable per unit transient reactance for an alternator rated 100 MW?
0.02 c. 1.0
0.3 d. 0.1
What should be the kV rating of a surge arrester to be used for an 11 kV ungrounded system?
18 kV c. 12 kV
16 kV d. 9 kV
Which of the following source of energy is not commercially used?
wind c. geothermal
solar d. biogas
If the stator voltage of a SCIM is reduced to 50 percent of its rated value, torque developed is reduced by ___ percent of its full – load value.
50 c. 57.7
25 d. 75
Two 60 Hz induction motors are connected in concatenation (cascaded). If machine 1 has 6 poles and machine 2 has 8 poles, the speed of the combination when the slip is 0.075 is ___ rpm.
514 c. 3,600
475 d. 1,110
A power station supplies 60 kW to a load over 2,500 ft of 000 2 – conductor copper feeder the resistance of which is 0.078 ohm per 1,000 ft. The bus – bar voltage is maintained constant at 600 volts. Determine the maximum power which can be transmitted.
60 kW c. 120 kW
230.7 kW d. 150 kW
Three units of 1:5 transformers are connected in /Y to supply three – phase load from a 400 volt, three – phase source. The line voltage on the load side is ___ volts.
2,000 c. 3,464
80 d. 80 3
Neglecting saturation, if current taken by a series motor is increased from 10 A to 12 A, the percentage increase in its torque is ___ percent.
20 c. 30.5
44 d. 16.6
Out of the following given choices for polyphase transformer connections, which one will you select for three to two phase conversion?
Scott c. double Scott
star/star d. star/double – delta
Two currents i1 and i2 whose values are given by the expressions i1 = 20 sin ωt and i2 = 15 sin (ωt + /4) are combined and made to pass through the common conductor. If the circuit has a resistance of 12 Ω, what will be the total energy loss in 10 hours?
62.929 x 103 J c. 2.646 x 108 J
2.266 x 108 J d. 26.46 x 108 J
For power transformers, the conservator tank is intended to minimize
heating c. oil slugging
internal pressure d. breathing
As referred to the Proposed Omnibus Power Act, IPP stands for:
Internal Power Plant
Individual Power Plants
Individual Power Protectors
Individual Power Producer
The PTR and CTR used to protect a line are 2,000 and 240, respectively. If the reactance as seen on the relay side is 1.41 Ω, what is the reactance of each line?
12.2 Ω c. 14 Ω
11.75 Ω d.16 Ω
When a bird lands on transmission lines, it is not electricuted because
no potential difference
bird s feet has high dielectric
no path for electric flow
bird s feather is an insulation
In a 10:1 step – down, 2200/220 V transformer, taps are changed to reduce the number of primary turns by 5%. The secondary voltage will most nearly be ___ volts.
209 c. 240
231 d. 225
A three –phase, 4 pole induction motor with open – circuited rotor is connected to a 400 V, 50 Hz, three – phase supply.
The motor will run at ___ rpm.
1500 c. 1450
1480 d. 0
The starting torque of a capacitor – start split phase induction motor is directly related to the angle between its two – winding currents by the relation
cos c. tan
sin d. sin /2
A certain four – terminal transmission device has a characteristic impedance of 600 ohms and a propagation constant of 0.5 + j1.0. When terminated with its
characteristic impedance, the ratio of the input voltage to the output voltage is what?
1.5 c. 0.5
1.65 d. 1.0
The line currents in a three – phase four – wire system are Ia = (300 + j400) A, Ib = (200 + j200) A and Ic = (-400 – j200) A. Determine the positive sequence component of Ia.
276 25.6° A c. 276 265.6° A
276 145.6° A d. 0
A system is consists of three equal resistors connected in delta and is fed from a balanced 3 – phase supply. By how much power is reduced if one of the resistors is disconnected?
a. 33% c. 50%
67% d. 25%
A balanced wye – connected load consisting of ZY = (3 + j4) /phase and a balanced delta – connected load having ZA = (9 + j12) /phase are connected to a 220 V three – phase source. On a per – phase basis, calculate the line current Ia.
50.8 53.13 A c. 5.08 173.13 A
50.8 173.13 A d. 5.08 53.13 A
The load on a three phase wye connected 220 V system consists of three 6 resistance connected in wye and in parallel with three 9 resistance connected in delta. The magnitude of the line current is
36.66 A c. 42.34 A
24.44 A d. 63.50 A
The apparent power input to a balanced wye – connected load is 30 kVA, and the corresponding true power is 15 kW at 50
A. The phase voltage is
346.4 V c. 230 V
400 V d. 200 V
Two purely resistive loads are connected to a 240 V three – phase, 3 – wire balanced supply. One of 4 kW is connected across lines A and B and the other of 6 kW is connected across lines B and C. The current in line B is
14.67 A c. 36.3 A
8.33 A d. 41.67 A
Three unbalanced 3Φ line voltages are given as follows:
VA = 10 cis 30
VB = 30 cis (-60 )
VC = 15 cis 145
What is the negative sequence component of line voltage VC?
8.24 cis (-156.2 ) c. 8.24 cis (-276.2 )
8.24 cis (-36.2 ) d. 0
A 440 V, 70 Hp shunt motor has an armature of 0.185 and field resistance of 350 . The current drawn by this machine is 135 A at full load. If this machine is to deliver torque equal to 175 per cent of that at full – load, what would be the resistance of its starter?
2 c. 1.695
1.2 d. 5.6
The initial rate of current rise in an RL circuit is 300 A/sec when 120 V is suddenly impressed. If the circuit resistance is 30 , what is the rate of current change when the current is 2.6 A?
300 A/sec c. 10 A/sec
105 A/sec d. 0.4 A/sec
A 230 V single phase meter has a constant load current of 4 A passing through the meter for 5 hours at unity power factor. If the meter disc makes 1,104 revolutions during this period, the meter constant in revolutions per kW-Hr is
240 c. 480
120 d. 360
The armature of a dc machine having 10 poles is rotating at a speed of 10 revolutions per second. The number of hysteresis loops formed per second is
100 c. 150
10 d. 50
A 5:1 ratio ideal transformer has a rated primary line voltage of 230 V. If a load impedance of 4 is connected across the secondary, what will be the primary impedance?
20 c. 1.25
100 d. 80
A 500 kVA, 13,200/240 V, three – phase transformer with an impedance of 4.2% is connected to an infinite bus and without load. If a three – phase fault occurs at the secondary terminals, the fault current in amperes is
26,040 A c. 24,680 A
26,840 A d. 28,640 A
A 3 phase balanced system working at 0.9 p.f. lagging has a line loss of 3,600 kW. If p.f. is reduced to 0.6, the line loss would become ___ kW.
8,100 c. 5,400
1,600 d. 4,800
A single transmission line has an impedance of (2 + j5) supplies a load of 50 kW at unity p.f. Find the voltage at the receiving end if the sending end is 2,400 volts.
a. 2,300 V c. 2,225 V
2,400 V d. 2,375 V
A 55,000 kW thermal power plant of NPC delivers an annual output of 283,000 MWHr with a peak load of 44 MW. The annual load factor of the plant is nearest to
0.75 c. 0.76
0.72 d. 0.73
If a generating station has a maximum load for the year of 18,000 kW and a load factor of 30.5%, how many units are generated for the year?
5,490,000 kW-Hr c. 59,016,000 kW-Hr
48,092,400 kW-Hr d. 4,590,000 kW-Hr
Presence of ozone as a result of corona is harmful because
it gives bad odor
it transfers energy to the ground
it reduces power factor
it corrodes the material
Two 1 , 25 kVA transformer are connected in open – delta bank. Determine the maximum kW the bank can supply
without overloading at 0.8 p.f. lagging
43.3 c. 40
34.64 d. 50
Two impedances given by Z1 = (10 + j5) and Z2 = (8 + j6) are joined in parallel and connected across a voltage of V = (200 + j0) V. What is the circuit power?
6,400 W c. 1,600 W
3,200 W d. 800 W
A distributor is designed from the point of view of
voltage drop
current carrying capacity
voltage drop and current carrying capacity
load capacity
The luminous intensity is defined as
lumen per square meter
luminous flux per unit solid angle
illumination per square meter
candela per unit solid angle
MHO relay is used for
rectifier c. transmission lines
circuit breakers d. feeders
In circuit breaker the time duration from the instant of fault to the instant of energizing of the trip coil is known as
lag time c. protection time
lead time d. operation time
Twenty tons of water are heated in 12 hours. If water is to be heated from 25 C to 95 C, find the kW rating of the heater if its efficiency is 92%.
147 c. 163
136 d. 174
What is the generated voltage in a 6 pole, 1200 rpm machine if its lap wound armature has 8 conductors in each of its 126 slots and a flux density of 57,000 lines per square inch exists over each pole face of 52.2 square inch?
60 V c. 300 V
120 V d. 600 V
A capacitor is charged by a steady current of 0.0012 amp for 25 sec. at which time its emf is 600 volts. What is the energy stored in the capacitor?
6 joules c. 9 joules
3 joules d. 12 joules
What is the output current in amperes corresponding to maximum efficiency for a transformer having core loss of 100 watts and equivalent resistance referred to the secondary of 0.25 ?
40 A c. 20 A
80 A d. 4 A
In transformer, the purpose of breather is to:
extract moisture of the air
to take insulating oil from conservator
to provide cooling to the winding
to provide insulation to the winding
What is the common unit of the sound absorption coefficient?
a. watt c. sabine erg d. decibel 502. The maximum power developed in a synchronous motor
occurs at a coupling angle of
0 c. 90
45 d. 180
The dc armature winding resistance between terminals of a 750 kVA, 4400 volt, three – phase alternator is 0.9 ohm.
Calculate the copper loss in the winding at the full –load.
13,075 W c. 26,149 W
16,343 W d. 10,800 W
It is also known as the polar graph of intensities of
illumination
Photometric brightness
Photosensor
Photometric report
Photometric distribution
What is the frequency range of the electrical equipment used to melt metals without the use of bunker fuel oil for induction heating?
500 – 1000 Hz c. 1 – 20 kHz
50 – 100 kHz d. 100 – 200 kHz
In a series motor, what is the relation of the connection of motor field winding with respect to the motor armature?
series c. series – parallel
parallel d. delta
If three transformers in - are delivering rated load and one transformer is removed, then what is the overload on each of the remaining transformer in percent?
173% c. 57.7%
73.3% d. 33.3%
A 6 pole, 60 Hz, 1140 rpm induction motor has a starting voltage of 120 volts across its rotor winding. What is its starting current in amperes if the rotor resistance is 5 and its blocked rotor reactance is 10 ?
24 c. 9.7
10.7 d. 12
What is the minimum number of magnetic contactors to allow forward – reverse control in the rotation of a motor?
4 c. 2
3 d. 1
What is the short – circuit temperature rating of cross –linked polyethylene (XLPE) cable in C?
150 c. 250
200 d. 300
What is the element of the transmission line that supports the cable at the bottom of the suspension insulator?
parallel clamp c. dead end clamp
suspension clamp d. strain clamp
The field circuit of a 4 pole dc generator has a resistance of 200 and an inductance of 100 H. If it is connected to a 400
volt supply, find the time taken for the current to reach 1.5 A
0.125 sec. c. 0.369 sec.
1.5 sec. d. 0.693 sec.
Calculate the effective voltage in one phase of an alternator, given the following particulars: f = 60 cps; turns per phase N = 240; flux per pole = 2.08 x 106.
1,330 V c. 1,225 V
2,304 V d. 2,122 V
When a circuit breaker is selected for a particular application, which one of the following ratings is usually considered the most important?
interrupting rating
continuous current rating
maximum rms current up to 1 second
maximum rms current up to 4 seconds
Which one of the following switchgear assemblies would most probably be used in a large industrial plant having several 600 volt meters, an air-conditioning system, and an extensive lighting system?
a low-voltage metal-enclosed switchgear
switchgear with SF6 circuit breakers
a station-type switchgear
a metal-clad switchgear
Periodic tests on protective relays are important to the stability of a system because the tests ensure that the: a. disconnect switches will work properly
"in" and "out" currents will be balanced
relays will operate in the proper sequence
arcing contacts can carry the main currents
If a fault occurs on substation high-voltage bus, the system is protected by a:
generator breaker
station feeder breaker
low-voltage power transformer breaker
high-voltage power transformer breaker
Which one of the following tests is preferred for checking switchgear insulation?
an arc high potential test
a dc high potential test
megometer test
a power factor test
In generating and distribution system, current balance is provided by protective zones which are:
used to eliminate reflections on short transmission lines
used to trip all circuit breakers I the system
isolated during fault by disconnect switches
monitored by differential relays
In switchgear application, the term "dead front" means that:
the front and rear panels are hinged
an access door is at the end of the structure
no equipment is mounted on the front panel
energized parts are not exposed on the front panel
The power flow between two electrical systems connected by tie lines is stabilized by the difference between:
voltage magnitude c. phase angles
current magnitude d. bearing temperatures
A circuit breaker that can be closed against a fault and operated at once, although the solenoid mechanism may continue through its closing operation, is said to be:
selective c. fully-rated
trip-free d. direct current operated
A large electric power distribution system is protected against surges and faults by:
protective gaps crossing drain coils
high-speed relays detecting the trouble
protective relays operating without a time delay
radio communication systems using flow frequency
If a 15-kV switchgear apparatus is used at an altitude of 1500 meters, the maximum applied voltage should be:
4900 volts c. 4750 volts
4800 volts d. 4000 volts
Which of the following steps is used for isolating a circuit breaker for maintenance purposes: a. pull the substation fuses
turn off the main generator
open the disconnect switches
ground the auxiliary
It is the reciprocal of the impedance:
conductance c. reactance
susceptance d. admittance
The impedance which when connected to one pair of terminals of a transducer produces a like impedance at the other pair of terminals:
characteristics impedance c. iterative impedance
input impedance d. surge impedance
In series circuit, resonance is defined as a condition which:
the net reactance to zero
total voltage is in phase with the current
the power factor is unity
all of the above
The product of the total voltage to the total current is:
total power c. reactive power
real power d. apparent power
In series RLC circuit at resonance, the current is:
zero c. maximum
minimum d. unity
In a variable resistant constant RL series circuit, the locus of the current is a:
straight line c. ellipse
parabola d. semi-circle
The Norton s equivalent circuit is a:
series circuit c. series-parallel circuit
parallel circuit d. parallel-series circuit
In any network of linear-bilateral impedances, a shift of source voltage E from one point in a circuit to a second is accompanied by a corresponding shift of current 1 from the second point to the first. This is known as:
Kirchhoff s laws c. Thevenin s theorem
Norton s theorem d. Reciprocity theorem
In a T method of measuring power in balanced 3-phase system using one wattmeter, total power is the wattmeter deflection multiplied by:
1 c. 1.732
2 d. 1.5
In the current transformer method of measuring power in balanced 3-phase system one wattmeter, total power is the wattmeter deflection multiplied by:
1 c. 1.732
2 d. 1.5
The order of rotation f the coil voltage in a balanced 3-phase system is called:
alternation c. phase shift
frequency d. phase sequence
A balanced two-phase system of voltages consists of two voltage which are equal and out of phase by:
30 degrees c. 120 degrees
90 degrees d. 150 degrees
In a 3-phase synchronous converter, the ratio of the ac voltage to dc voltage is:
1.0 c. 0.612
0.707 d. 0.50
A non-sinusoidal wave is symmetrical if it is made up only of:
dc component c. even harmonics
triangular wave d. odd harmonics
An exchange of conductor positions in transmission line is called:
alternation c. transposition
bundling d. interpolation
A line terminal in its characteristic or surge impedance is called:
incident line c. attenuated line
reflected line d. flat line
The total input to the armature at no load minus the armature resistance loss is:
power developed in the armature
stray load
stray power
shunt field loss
It is the power required to drive the unexcited dc machine at normal speed with its brushes lifted: a. Friction and windage loss
Brush friction loss
Exciter loss
Ventilation loss
When a circular breaker is selected for a particular application, which one of the particular ratings is usually considered most important?
interrupting rating c. momentary rating
continuous rating d. maximum current rating
In starting a 500hp, 2300 volt, 3-phase synchronous motor the field winding is initiallly short circuited so as to: a. produce much larger starting torque
lower voltage produced between layers of the field winding
increased induced voltage in field winding
provide better flux distribution in the air gap
The ratio of the average load on the plant for the period of time to the aggregate rating of all generating equipment: a. plant use factor c. power factor
b. capacity factor d. maintenance factor
The ratio of the individual maximum demands of the systems to the overall maximum demand of the whole system: a. load factor c. utilization factor
b. diversity factor d. demand factor
In parallel operation of alternators, if the excitation of one alternate is changed it will only change: a. real power taken by the machine
reactive power taken by the machine
apparent power taken by the machine
synchronizing power of the machine
In a medium or long line when operated at no load or loaded very slightly, the receiving end will be found greater than the sending end voltage. This phenomenon is known as:
Skin effect c. corona
Ferranti effect d. Thevenin s theorem
For parallel operation of dc generators:
the frequency must be the same
the voltage must be the same
phase sequence must be the same
speed must be the same
The simplest form of motor controller is:
toggle switch c. manual starter
magnetic switch d. magnetic control
Another name for the magnetic starter is a:
manual switch c. manual starter
contactor d. magnetic control
A 15A fuse is found open, but the services do not have a replacement and has a choice between a 10A and 30 A fuse.
Use the:
10A fuse c. 40A fuse
30A fuse d. 20A fuse
What type of overload contains a solder pot?
melting alloy c. magnetic
bimetallic d. fuse
What type of overload operates on the principle of electromagnetism?
melting alloy c. magnetic
bimetallic d. fuse
Low voltage often causes the magnetic control to:
gum up c. chatter
run more efficiently d. none of the above
Rapid stopping of a motor by momentarily connecting the motor in reverse direction is called:
togging c. plugging
inching d. sequence operation
A hot smokey transformer indicates a/an
open c. both (a) and (b)
short d. none of the above
A sorted motor will draw _____ current
low c. both (a) and (b)
high d. none of the above
3-phase manual-starting switches are sometimes used to turn on or off motors up to ______ horsepowers.
5 c. 15
10 d. 20
The device used to control a motor from a distant location is the:
manual starter c. magnetic controller
drum switch d. snap switch
Which of the following devices is a type of timer?
interval c. percentage
pulse d. all of the above
The device that controls the flow of air back into chamber of the pneumatic time relay is the:
diaphragm c. shading coil
needle valve d. all of the above
If the motor runs but fails to stop, the problem may be:
open fuse
welded holding circuit interlock
jogging or plugging duty overload
none of the above
If the motor runs at half speed or "sits and hums", look for ________ in the magnetic controller: a. an open phase
welded holding circuit interlock
both (a)and (b)
none of the above
Repeated starting and stopping is referred to as:
stepping c. phasing
jogging d. long acceleration time
A chattering or humming in magnetic contactor may be due to:
broken shading coil c. both (a) and (b)
dirty/worn contacts d. none of the above
Which of the following contacts should not be piled?
cadmium-plated c. both (a) and (b)
silver-plated d. none of the above
The minimum ampere capacity panel box used today is:
30 c. 100
60 d. 150
Number 8 wire is generally used for _______ amps:
15 c. 30
20 d. 40
Another name for emt is:
nonmetallic cable c. conduit
flexible metallic cable d. armored clad cable
Another name for flexible steel cable is:
conduit c. synthetic cable
emt d. nonmetallic
The common neutral wire is usually ______ in color and connected to a:
black; cold water pipe
white; circuit breaker or fuse
black; circuit breaker or fuse
white; cold water pipe
A 4-way switch controls a lamp from _____ different locations:
1 c. 3
2 d. 4
The power factor rating of an inductive reactive circuit can be increased by adding:
capacitors c. coils
inductors d. fuses
The device used to pull wire through conduit is called:
wire tongs c. connectors
straps d. fish tape
The best way to check insulation resistance is with a:
voltmeter c. ammeter
ohmmeter d. megohmeter
To decrease signal strength in strong signal areas use a:
splitter c. coupler
amplifier d. attenuator
Which of the following lamps uses a starting switch?
preheat c. instant heat
rapid heat d. all of the above
Which of the following lamps requires a cooling period prior to restarting?
incandescent c. mercury vapor
fluorescent d. none of the above
The device used to attenuate specific signals is the:
drop tap c. splitter
line tapoff d. trap
The wire that is shielded is:
flat twinlead c. coaxial
foam-filled twinlead d. all of the above
Which of the following wires has 75-ohm impedance:
flat twinlead c. coaxial
foam-filled twinlead d. none of the above
The maximum capacity for a general 20A general-purpose appliance circuit is approximately:
1500 watts c. 2400 watts
1800 watts d. 2800 watts
The type of thermostat most commonly used in appliance with heating elements is the:
magnetic relay c. bimetallic
circuit breaker d. all of the above
Most heating appliances use a cord made of:
rubber c. both (a) and (b)
asbestos cover d. all of the above
Insulators are commonly made of:
ceramic c. porcelain
mica d. all of the above
Most cordless electric slicing knives use a charge unit and:
rectifier c. diode
battery pack d. none of the above
Heating elements can be repaired by a ______ tube which crimps the two broken elements together:
nickel/silver c. wire
aluminum d. aluminum/nickel
Most heating elements can be checked by using a/an:
ammeter c. ohmmeter
wattmeter d. growler
One of the most common problems of a hair blower/styler is defective:
cord c. thermostat
transistor d. SCR
An overheated cord often indicates:
corroded terminals c. both (a) and (b)
defective cord d. none of the above
The insulation used in most water heater is:
fiberglass c. both (a) and (b)
rock wool d. none of the above
When examining a dead set, which item(s) should be checked?
power supply diodes c. open filament
fuse d. all of the above
The decibel reading for proper separation between channels of multiplex unit is:
50 dB c. 20 dB
10 dB d. 40 dB
If only none of the transistors is a push-pull, amplifier is bad:
replace only the bad one c. (a) or (b)
replace both of them d. none of the above
When using an ohmmeter to identify a short, the ohmmeter reading should indicate:
zero c. 100 kilo ohms
infinite d. 1 mega ohms
Is used to change the sequence in which the units may be placed in and out of service in multiple unit equipment: a. reversing switch c. accelerating switch
b. starting switch d. unit sequence switch
To join two rigid steel conduits use:
tape c. clamp
coupling d. locknut
The power factor of an induction motor is:
leading c. lagging
unity d. zero
A lamp maybe controlled from three different points by:
2-way c. 3-way
4-way d. selector
Electromotive force is measured by:
ammeter c. ohmmeter
voltmeter d. wattmeter
This refers to the circuit conductor between the series equipment and the branch circuit over current device: a. service drop c. service entrance
b. feeder d. secondary
One advantage of the aluminum over copper wire is:
higher ampacity c. available commercially
higher resistance d. cheaper
This device converts as to dc:
inverter c. compensator
rectifier d. transformer
The unit by which electric energy is sold is the:
kW-hr c. ampere-hr
W-hr d. lumens
Ohm is the unit of:
capacitance c. power
reluctance d. resistance
Burrs on sharp edges in the inside of a rigid steel conduit end are removed with the use of:
reamer c. knife
wrench d. plier
It is a lubricant that is used to make pulling wires/cables through conduit easier:
resin c. talc
iron filing d. grease
One horsepower is approximately:
2000 watts c. 750 watts
1500 watts d. 850 watts
It is a device that is used to interrupt fault current without injury to itself:
fuse c. cut-out
circuit breaker d. regulator
It is used for direct measurement of electrical insulation:
megger c. micrometer
volt ammeter d. growler
30A is one of the five special branch circuits rating with a circuit conductor of:
2 mm2 c. 5.5 mm2
3.5 mm2 d. 8 mm2
The unit of an electrical system which is intended to carry but not utilize electrical energy is:
device c. serving drop
branch circuit d. service equipment
The main contacts of circuit breaker are most likely to be operated by a:
vacuum c. mimic rays
solenoid d. heavy duty switch
In switch gear application, the term "dead front" means that:
the front and rear panels are hinged
an access door is at the end of the structure
no equipment is mounted on the front panel
energized parts are not exposed on the front panel
The current that a breaker must be able to carry immediately after a fault occurs is known as:
interrupting current c. exciting current
short-circuit current d. momentary current
There is no zero sequence component of the fault current for:
symmetrical fault
single line to ground fault
line to line ground fault
double line to ground fault
When the primary and secondary windings take the form of a common ring which is encircled by two or more rings of magnetic material distributed around its periphery, the transformer is termed as: a. grounding transformer
regulating transformer
core type transformer
shell type transformer
When alternating current is passing through a conductor here is a tendency for the current to crows near the surface of the conductor. This is known as:
corona c. resistivity
skin effect d. magnetization
Ratio of lumens reaching the work plane divided by the total lumens generated by the lights: a. coefficient of utilization
illumination factor
maintenance factor
room ratio
The inner strand of ACSR cable is made of:
copper c. lead
brass d. steel
It is used to join a length of conduit with another:
tape c. bushing
coupling d. clamp
Pin insulators are made of:
paper c. mica
porcelain d. copper
A complete path over which an electric current can flow is:
load c. circuit
transmission line d. resistance
The power factor of an induction motor is:
leading c. zero
100% d. lagging
Branch circuit conductors applying a single motor shall have an ampacity of not less than ______ percent of full load current rating:
125 c. 150
115 d. 200
In house wiring, grounded conductors must not be:
fused c. placed in conduit
insulated d. mechanically protected
Which of the following materials is the best conductor of electricity?
nichrome c. tungsten
aluminum d. copper
What test is commonly made on cables after insulation:
insulation c. conductance
resistance d. impedance
What is the maximum number of quarter bends (90 degrees) allowed in rigid metal conduit wiring between boxes?
no limit c. 3
2 d. 4
It is a point in the wiring system at which current is taken to supply utilization equipment:
junction box c. feeder
pull box d. outlet
To protect a circuit from circuit conditions, ________ is used:
recloser c. disconnect switch
fuse d. alarm
What will happen if a 230 volt airconditioner is connected to a 115 volt line?
current will be less than normal
it runs slower
it will burn out
it will overspeed
Ampacity of No. 14AWG TW, three wire copper conductor cable at 30° ambient is:
15 amperes c. 25 amperes
20 amperes d. 30 amperes
Split knobs are made of:
wood c. copper
brass d. porcelain
A device with a blank cover in a run of raceway to facilitate pulling in of conductors is the:
coupling c. outlet box
elbow d. bushing
In an AC circuit, current equals:
E/R c. E2
IR d. E/Z
AC voltages may be increased or decreased by means of /an:
induction motor c. rheostat
transformer d. rectifier
An ammeter is connected:
across c. series
in conjunction d. series or parallel
To determine the positive wire in a single phase ac circuit:
use a neon lamp tester
use an ammeter
use a phase sequence meter
is impossible
Which of the following is the smallest size wire?
No. 20 c. No. 2
No. 10 d. No. 00
In open wire installation, the wires are supported on:
post insulators c. strain insulators
tubes d. knobs
Which of the following can reduce starting current of a large ac motor?
magnetic starter c. compensator
capacitor d. rectifier
No wire smaller than number _______ is allowed for general interior wiring:
12 c. 16
14 d. 18
The power factor of a circuit is approximately 100% if the circuit load consists only of:
reactance coils c. motors
capacitors d. incandescent lamps
A mill is equal to:
0.001 of an inch c. 0.745 of an inch
one inch d. none of the above
The filament of incandescent lamps is made of:
copper c. aluminum
silver d. tungsten
Operating stick for disconnect switches is made of:
Steel c. wood
aluminum d. brass
The common dry cell gives a voltage of about:
1 volt c. 1.5 volts
10 volts d. 3 volts
A transformer or generator inserted in a circuit to correct the voltage is called:
rheostat c. ohmmeter
current transformer d. potential transformer
It may be used to identify blown out fuses in a live circuit:
ammeter c. ohmmeter
voltmeter d. test lamp
The relationship between voltage, current and resistance in a dc circuit is called:
Boyle s law c. Kirchhoff s law
Kelvin s law d. Ohm's law
It is used for transformer cores:
cast iron c. brass
steel d. aluminum
Which appliance has the largest consumption of electricity?
radio c. air conditioner
television d. toaster
A megger us used to measure:
insulation resistance c. conductance
inductance d. capacitance
It is used to measure the diameter of wires:
micrometer c. caliper
spring balance d. wire gauge
What kind of motor can be reversed by interchanging any two leads?
split phase c. series
shunt d. three phase
What are used on the outside of the box whenever the
conduit enters an outlet box
bushing c. couplings
locknuts d. elbows
It is used to correct the power factor of fluorescent lamp?
rectifier c. starter
varmeter d. capacitor
It refers to the circuit conductors between the service equipment and the branch circuit over current device: a. service drop c. service entrance
b. feeder d. secondary
It is an enclosure for surface or flush mounting with a frame in which swinging doors are hung:
raceway c. cabinet
switchboard d. outlet
Comparing No. 12 and No. 18 bare copper wires of equal length, the No. 12 wire will have lower:
weight c. iron
resistance d. carbon
If a fuse of higher than required current rating is employed in a circuit, it will:
blow more frequently since it carried more current
afford better protection to the circuit
seriously overload the circuit
lead t larger maintenance
For flexible cable, most suitable insulation is:
magnesium oxide c. insulation tape
glass fiber d. polyvinyl chloride
Out of the following, select the best conductor of electricity:
graphite c. porcelain
china clay d. none of these
The specific resistance p is defined as:
resistance of a conductor which has a length of 1m and cross-section 1m2 at 25°C
resistance of any conductor at 25°C
resistance of any conductor at 20°C
resistance of a conductor which has a length of 1m and a cross-section of 1cm2 at 25°C
The value of joules mechanical equivalent of heat J, is equal to:
4.2 calories per joule
4.2 calories per calorie
2.4 joules per calorie
4.2 joules
Which of the following material has nearly zero temperature coefficient of resistance?
carbon c. copper
porcelain d. manganin
A buffer battery is used for:
the same purpose as floating battery
interconnecting dc generator and standby battery
trickle charge
decreasing variations of the voltage and the current supplied by dc generator
The scale of an indicating instrument whose each division represents the same value is known as ______ scale:
digital c. numbered
square law d. linear
Rotating field instrument is a/an ______ instrument:
thermal c. electrodynamic
bimetallic d. induction
For maximum power transfer according to maximum power theorem source impedance:
must be very much larger as compared to the load impedance
must be complex conjugate of lad impedance
must be very small as compared to the load impedance
must be equal to load impedance
An instrument which is used for measuring temperature variations by change in metallic resistance is called a:
thermopile c. bolometer
thermocouple d. thermo-galvanometer
The instrument which is used for determining the magnetic characteristics of ferr0-magnetic substances is called a:
flux meter c. permeameter
magnetometer d. hysteresis meter
Ondograph is an instrument which is used for recording:
wave shape of voltage or current
instantaneous value of voltage or current
over voltages with the help of brush discharge
synchronism of two ac voltages or voltage systems
In the list below, which is not a type of present day nuclear power plant?
boiling water reactor
low pressure reactor
fusion fission reactor
fast breeder reactor
A device which measures speed while flashing at a pre-set frequency is called a:
stroboscope c. electroscope
oscilloscope d. synchronoscope
Nuclear fission is similar to fusion in the sense that it also:
involves neutrons
is initiated by protons
needs high temperature
results in release of large amount of energy
Piezo electricity principle is applied in one of the following:
ultrasound equipment c. microphones
thermometer d. TV sets
The condition in Ohm s law is that:
ration V/l should be constant
current should be proportional to voltage
the temperature should remain constant
the temperature should vary
When current flows in a conductor, heat is produced because:
heat a l2 c. of interatomic collision
of electronic collision d. of Joule s law
Ohm s law is applicable to:
electric arc c. gas discharge lamps
rectifying devices d. none of these
Ohm s law can be applied with certain reservation to:
rectifiying devices c. electrolytes
semiconductors d. thermionic valves
Resistors commonly used in power circuits are:
carbon resistor c. wire wound resistors
etched circuit resistors d. deposited metal resistors
The combined resistance of two equal resistors connected in parallel is equal to ______ to the resistance of one resistor:
one half c. four times
twice d. one fourth
The voltage drop per ampere-meter of an aluminum conductor is higher as compared to a copper conductor of the same size due to its higher:
insulation resistance c. conductivity
resistivity d. current density
A natural magnet is called:
steel c. magnetism
lodestone d. soft iron
Externally, magnetic line of force travel:
south to north c. north to south
negatie to positive d. in both directions
A material commonly used for shielding or screening magnetism is:
brass c. copper
aluminum d. soft iron
Bakelite is classified as:
flammable c. combustion resistant
incombustible d. semiconductor
In most electric irons, the thermostat used for controlling temperature is:
vapor-filled tub c. high-expansion steel rod
bimetallic strip d. thermopile
If a 220V heater is used on 110V supply, heat produced by it will be as ______ much:
one half c. one fourth
twice d. four times
The current carrying capacity of a Cu wire having the twice the diameter of another Cu wire as _____ as great:
twice c. half
four times d. three times
For a given line voltage, four heating coils will produced maximum heat when connected: a. all in parallel
all in series
with two parallel pairs in series
one pair in parallel with the other two in series
The electric energy required to raise the temperature of a given amount of water is 1000 kWh. If the heat losses are 25%, the total heating energy required is kWh.
1500 c. 1333
1250 d. 1000
Nichrome is commonly used for:
lamp filaments c. heater coils
transformer d. battery connections
Iron becomes magnetized by induction when it is:
heated
near to one end of a magnet
suspended east and west
treated with some chemicals
Maxwell s loop current method of solving electrical networks:
uses branch currents
utilizes Kirchhoff s voltage law
is confined to single-op circuits
is a network reduction method
Testing a blown cartridge fuse by connecting a test lamp from one slip to the other of the suspected fuse will always indicate a:
blown fuse if lamp remains dark
blown fuse if lamp lights up
good fuse if lamp lights up
good fuse if lamp remains dark
For testing insulation between the heating element and the body of an electric iron, you would preferably use:
ohmmeter c. megger
lamp and battery tester d. capacitor bridge
Kirchhoff s voltage law (KVL) is connected with:
IR drops c. junction voltages
battery efms d. both (a) and (b)
Superposition theorem can be applied only to circuits having _______ elements:
non-linear c. linear
passive d. resistive
Permeance is analogous to:
conductance c. reluctance
resistance d. none of these
When the magnetic flux (Ø) and the area (A) under its influence are known, the magnetic flux density (B) can be given as:
B = Ø X A c. B = A / Ø
B = Ø / A d. B = Ø x A2
The relative permeability of paramagnetic substance is:
slightly less than 1
equal to 1
slightly greater than 1
very much greater than 1
The magnetization in any magnetic material appears as a result of:
electrons orbital motion
electron spin
spin of the nucleus about its axis
all of these
Which of the following materials does not have permanent magnetic dipole:
Paramagnetic c. diamagnetic
anti-ferromagnetic d. ferromagnetic
Interaction between the neighboring dipoles is negligible in case of:
paramagnetic material
diamagnetic material
anti-ferromagnetic material
ferromagnetic material
Each Ferromagnetic material has characteristic temperature above which its properties are quite different from those below the temperature. This temperature is called: a. Transition temperature
Faraday s temperature
Demagnetization temperature
Curie temperature
The relative permeability u for iron is:
5000 c. 3000
7000 d. 1000
Which of the following material is used for making permanent magnets:
Carbon steel
Platinum cobalt
Alnico V
All three mentioned above
Which of the following statement is correct?
Whenever the flux linking with the coil or circuit changes emf is produced
The direction of dynamically induced emf can be determined by Flemings right hand rule
Coefficient of coupling for tightly coupled coil is zero
The coefficient of self-inductance is proportional to the square of number of turns on it
Ferromagnetic materials generally behave as a:
semi-conductor c. insulator
conduction d. any a,b or c
Eddy current loss can be minimized by:
decreasing the resistance of magnetic medium
increasing the resistance of magnetic medium
decreasing the permeability of magnetic medium
none of these
A collapsing field around a coil:
tends to oppose the decay of coil current
helps the decay of coil current
tends to aid current flow reversal
does not effect the coil current flow
Which of the following is a vector quantity?
magnetic potential c. magnetic field intensity
flux density d. relative permeability
Whenever a conductor cuts magnetic flux, an emf is induced in that conductor. Above statement is due to:
Joule s law c. Faraday's law
Coulomb s law d. Weber and Ewings theory
In the left hand, thumb always represents:
voltage
current
direction of force on conductor
magnetic field
While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electric circuit?
emf c. conductivity
current density d. current
The law that induces emf and current always opposes the cause producing them was discovered by:
Lenz c. Maxwell
Farady d. Ohm
The location of lightning arrester is:
near the transformer
near the circuit
away from the transformer
none of the above
Iron core material of inductors used in radio at high frequencies:
is laminated
has low permeability
reduces inductances as well as losses
is called ferrite
Air-gap in the iron core of an inductor prevents:
core saturation c. flux leakage
hysteresis loss d. transformer
The time constant of an inductive circuit is defined as the ratio of:
R / L c. Lt / R
Rt / L d. L / R
The coupling coefficient denotes:
the degree of magnetic linkage
whether the reluctance remains constant
the variation of inductance between the two coils
whether the flux linkage is constant
It is difficult to magnetize steel because of its:
low permeability c. high permeability
high retentivity d. high density
Hysteresis losses can be reduced by:
using grain-oriented silicon steel
increasing the frequency of the field
laminating the core
none of these
The purpose of shielding a meter with soft iron is to:
prevent damage rough use
keep moisture out of movement
protect meter movement from stray magnetic fields
achieve all of the above
A solid piece of iron:
is less desirable than a laminated core
is an excellent core material for low frequencies
reduces losses in an inductor
is the only suitable core for radio frequencies
The hysteresis loss can be minimized by selecting a magnetic material having:
large B /H loop area
high resistivity
high retentivity
low hysteresis coefficient
The hysteresis loss in a given specimen of a magnetic material may be decreased by:
increasing flux density through it
increasing frequency of reversal of magnetization
laminating it
decreasing maximum flux density established through it
In electrical machines, laminated cores used with view to reducing:
hysteresis loss c. friction loss
eddy current loss d. copper loss
The process by which metallic parts are demagnetized is called:
demagnetizing c. degrading
degaussing d. degreasing
The absolute permitivity of vacuum is taken as:
8.854 x 10-6 farad/m c. 8.854 x 10-9 farad/m
8.854 x 10-12 farad/m d. none of the above
The unit of field intensity is:
coulomb c. newtons/coulomb
coulomb/m2 d. None of the above
If a test lamp lights up when connected in series with a capacitor and a suitable dc supply, it clearly shows that the capacitor is:
short-circuited c. fully-discharged
fully-charged d. open-circuit
The electrical equipment occasionally connected across relay contacts for minimizing arcing is a/an:
resistor c. carbon tip
inductor d. capacitor
A charge of 100 coulombs are transferred I a circuit by a current of 1A. Time taken by this current is ______ seconds:
1 c. 100
10 d. 1000
One of the best ways to check for an open electrolytic capacitor in a circuit is to:
temporarily connect a known good capacitor across it
remove it and insert a good one
measure d voltage across it
use capacitor checker
Which one of the following types of capacitor is polarized?
electrolytic c. paper
ceramic d. mylar
Present day capacitors which have high capacitance in small size use a dielectric of:
paper c. ceramic
rubber d. mylar
Dielectric strength of a material depends on:
moisture content c. temperature
thickness d. all of the above
Which medium has highest value of dielectric strength?
glass c. porcelain
mica d. quartz
Capacitors are said to
block ac and pass dc c. pass ac and dc
block dc and pass ac d. block ac and dc
The effect of the dielectric is to
increase the capacitance
decrease the capacitance
reduce the working voltage
increase the distance between the plates
One farad is
coulomb-Joule c. Joule per volt
one coulomb per volt d. one volt per coulomb
The power dissipated in a pure capacitor is
maximum
minimum
zero
depends on the size and voltage
In a capacitor, the electric charge is stored in
metal plates
dielectric
dielectric as well as metal plates
none of the above
If a dielectric is placed in an electric field, the field strength
decreases c. remain the same
increases d. becomes zero
A capacitance C is charged through a resistance R. The time constant of the charging circuit is given by
RC c. C/R
1/(RC) d. R/C
A circuit component that opposes the changes in the circuit voltage is
resistance c. capacitance
inductance d. none of the above
The mass of an ion liberated at an electrode is directly proportional to the quantity which passes through the electrolyte. The above statement is associated with
Gauss theorem c. Weber and Ewing s theory
Laplace law d. Law of electrolysis
In electroplating, the positive electrode is called the
cathode c. anode
terminal d. iontrap
One factor affecting voltages of the primary cells is the
area of the plates
distance between the plates
types of plates and electrolytes
thickness of the plates
The condition of a liquid electrolyte is measured in terms of
its
current value c. acid content
specific gravity d. voltage output
The action in the primary cell can be rectified by
chemical action to mechanical energy
chemical action to electrical energy
electrical energy to mechanical energy
electrical energy to magnetic energy
The two main effects of the primary cell are
polarization and sulfation
local action and polarization
bucking and polarization
sulfation and bucking
Cells are connected in parallel to
increase the internal resistance
decrease the current capacity
increase the current capacity
increase the voltage output
The composition of secondary cell is
zinc, copper and dilute sulfuric acid
zinc, carbon and dilute sulfuric acid
lead, lead peroxide and dilute sulfuric acid
none of the above
The condition of a secondary cell can be determined by
its terminal voltage
the color of the electrolyte
level of the electrolyte
the terminal voltage and strength of the electrolyte
Electrolyte of a storage battery is formed by adding
water to hydrochloric acid c. hydrochloric acid to water
sulfuric acid to water d. water to sulfuric acid
Lead is the metal which is commonly used for
transformer core c. electromagnets
storage batteries d. knife-switch blades
When liquid level in a lead-acid cell is low, the proper remedy
is to
add only distilled water
add weak acid solution
empty out the cell and replace the entire solution
do nothing till plates becomes fully exposed
The active materials on the positive and negative plates of a fully-charged lead-acid cell are
lead peroxide and pure lead
pure lead and lead sulfate
lead peroxide and lead sulfate
pure lead and pure lead
A lead acid battery should not be left in discharged state for long otherwise
acid will evaporate
plates will become sulfated
electrolyte will start attacking the plates
terminals will get corroded
When making new electrolyte by mixing sulfuric acid and water, acid should be poured into water to avoid a. corrosion of mixing vessel
use of too much acid
making initial mixture too weal
generation of excess heat
A battery:
always absorbs water
always delivers power
can absorb or deliver power depending upon the circuit to which it is connected
absorbs power when the internal resistance is non-zero but delivers power when the internal resistance is zero
Which of the following gives best indication of a fully-charged battery?
open-circuit cell voltage
level of electrolyte specific gravity temperature of the electrolyte 770. A battery is said to be floating on the battery-bus when
its supplied at the load
its voltage is higher than the bus voltage
charger is shut down
battery voltage equals the charger voltage
The storage battery most commonly used in industry today is _______ battery:
silver-zinc c. zinc cadmium
lead acid d. nickel cadmium
Distilled water is variably used in electrolytes because it:
prevents polarization
prevents local action
accelerates electrochemical action
improves specific gravity of the electrolyte
The action of all batteries is dependent on:
dilute sulfuric acid c. electrochemical action
electrolysis d. lead peroxide
High battery voltages can be obtained by:
connecting cells in series
connecting cells in parallel
using large size cells
increasing quantity of electrolyte
The specific gravity of a lead-acid cells is often used as a measure of its:
rate of discharge c. state of charge
operating temperature d. life expectancy
The sole purpose of using separators in a storage battery is to prevent the plates from:
touching the container c. shorting together
touching the electrolyte d. shorting to the bottom
The most important advantage of nickel-cadmium battery over a nickel-iron battery is its:
higher voltage
greater strength ability to hold a charge all of the above
The most common impurity found in the battery electrolyte is:
sodium chloride c. lead
iron d. dust
Excessive overcharging of a lead-acid battery will cause:
increased internal resistance
excessive gassing
loss of water
all of the above
Main difference between primary and secondary cells is that secondary cells:
give higher voltage c. store electric charge
absorb hydrogen d. can be charged
The ampere hour capacity of battery depends on:
the thickness of the plates
the area of the plates
the strength of the electrolytes
the distance between the plates
The internal resistance of a discharged battery:
is more c. remains constant
is less d. is negative
A partially discharged lead storage lead storage battery may be brought back to full charge by: a. adding sulfuric acid
adding distilled water
applying ac voltage across the terminal
applying dc voltage across the terminal
Charging a lead-acid cell causes the electrolyte to become :
stronger c. weaker
stable d. water
A cell which is used as voltage reference source for instrument calibration is:
solar cell
dry cell
mercury-cadmium cell nickel-cadmium cell
A fuel cell converts _______ energy into electrical energy:
mechanical c. chemical
magnetic d. solar
The output voltage of a single loop generator is a:
steady dc c. pulsating dc
steady ac d. pulsating ac
What effect on current flow does reversing the direction of movement of a conductor in the magnetic field of a generator have :
neutralizes the current flow
has no effect on current
it reverses the direction of current flow
none of the above
In most generators the output voltage is induced by:
rotating magnetic field past stationary coils
relative motion between the field and the armature coils
converting electrical energy into mechanical energy
none of the above
What classification is given to a dc generator that receives its field excitation current from internal source?
self-excited c. separately-excited
controlled excite d. internally excited
The shunt filed of a compound generator is connected across both series field and the armature. This connection is known as:
short shunt c. differential compound
long shunt d. cumulative compound
In a DC generator, the flux is seen to be _____ at the trailing pole tips and also ______ at the leading pole tips:
weakened, weakened c. crowded, weakened
weakened, crowded d. same, same
Electric dc generators have normally, an overall efficiency of the order of:
60-80% c. 80-90%
75-85% d. 85-95%
Residual magnetism is necessary in a:
separately excited generator
self excited generator
both of these
none of these
The armature magnetic field has effect that:
it demagnetizes or weakens the main flux
it cross magnetizes, or distorts it
it magnetizes or strengthens the main flux
(a) and (b)
In the commutation process it is the:
current which is getting reversed
voltage which is getting reversed
both of these
none of these
In any DC generator, the emf generated in the armature is maximum when:
rate of change of flux linked is minimum
rate of change of flux is maximum
flux linked with conductor is maximum
flux linked with conductor is minimum
A simple method of increasing the voltage of a DC generator is:
to decrease the air gap flux density
to increase the speed if rotation
to decrease the speed of rotation
to increase the length of the armature
The function of interpole or compole is:
to neutralize the reactance voltage and help in commutation process
to neutralize the cross-magnetizing effect of armature reaction
to neutralize the demagnetizing effect of the armature
(a) and (b)
Critical resistance of a DC generator Rc
Rc α (speed)-1 c. Rc α (speed)2
Rc α (speed) d. Rc α (speed)-2
Interpoles are connected in _____ with the armature and compensating windings are connected in _______ with the armature:
series, series c. shunt, series
series, shunt d. shunt, shunt
Generators are often preferred to be run in parallel because of having the advantages of: a. great reliability
generator efficiency
meeting greater load demands
all of the above
Shunt generator are used where the main requirement is a constant:
current and voltage
current
voltage over a wide load range
voltage over a narrow load range
Equalizer connections are required when paralleling two:
compound generators c. shunt generators
series generators d. none of the above
Interpoles are normally connected in:
parallel with the field c. parallel with the field
series with the field d. series with the load
DC generator preferred for charging automobile batteries is:
shunt generator
series generator
long shunt compound generator
none of the above
Which loss in DC generator varies with the load
copper loss c. hysteresis loss
eddy current loss d. windage loss
The armature of a DC generator is laminated to:
reduce the bulk
insulate the core
reduce eddy current loss
provide passage for cooling air
In a shunt generator, the voltage built up generally restricted by:
speed limitation c. saturation of iron
armature heating d. none of the above
With DC generator, which of the following regulation is preferred:
1% regulation c. infinite regulation
50% regulation d. 100% regulation
The function of the commutator in a DC generator is:
to change alternating current into direct current
to improve commutation
for easy speed control
to change alternating voltage into direct voltage
Carbon brushes are used in electric motors to:
brush off carbon deposits on the commutator
provide a path for flow of current
prevent overheating of armature windings
prevent sparking during commutation
The speed of a DC motor is:
directly proportional to back emf and inversely proportional to flux
inversely proportional to back emf and directly proportional to flux
directly proportional to emf as well as flux
inversely proportional to emf as well as flux
An external resistance is added in the series with the field of a DC shunt motor. When the motor runs, the effect of resistance:
to reduce the speed of the motor
to increase the speed of the motor
to reduce the armature current drawn by the motor
to reduce the losses
If the speed of the DC shunt motor increases, the back emf:
increases
decreases
remain constant
decreases and then increases
In a DC motor iron losses occur in:
the yoke c. the field
the armature d. none of these
The current flowing in the conductors of a DC motor will:
AC c. AC as well as DC
DC d. transients
As the load is increased, the speed of a DC shunt motor will:
remain constant c. increase slightly
increase proportionately d. reduce slightly
One DC motor drives another DC motor. The second DC motor when excited and driven: a. runs
does not run as a generator
runs as a generator
also runs as a motor
In dc shunt motors, if the terminal voltage is reduced to half and torque remains the same, then:
speed will be half and armature current also will be half
speed will be half but armature current remains the same
speed will be half and armature current becomes double
speed and armature current will remain the same
The torque of a motor is:
the force in N-m acting on the rotor
the product of tangential force on the rotor and its radius
the electrical power in KW
the power given to load being driven by the motor
The power stated on the name plate of any motor is always:
the output power at the shaft
the power drawn in KVA
the power in KW
the gross power
The speed of a series motor at no load is:
Zero c. 1800 rpm
3000 rpm d. infinity
A starter is necessary to start a DC motor because:
it starts the motor
it limits the speed of the motor
it limits the back emf t a safe value
it limits the starting current to a safe value
The direction of rotation of a DC motor is reversed by:
reversing armature connections
interchanging the armature and field current
adding resistance to field current
reversing supply connection
Which of the following is a correct statement about a series motor?
its field winding consists of thicker wire and less turns
it an run easily without load
it has am almost constant speed
it has poor torque
If the back emf in a DC motor is absent, then:
motor will run at very high speed
motor will run at very low sped
motor will not run at all
motor will burn
A series motor is started without load. The effect is that:
the torque increases rapidly
the speed increases rapidly
the current drawn increases rapidly
the back emf decreases
If the field of a DC shunt motor is opened:
it will continue to run at its rated speed
the speed of the motor will become very high
the motor will stop
the speed of motor will decrease
Interpoles are meant for:
increasing the speed of the motor
decreasing counter emf
reducing sparking at the commutator
converting armature current to dc
Armature reaction is attributed to:
the effect of magnetic field set-up by the armature current
the effect of magnetic field set-up by field current
copper loss in the armature
the effect of magnetic field set-up by the back emf
When the electric train is moving down a hill the DC motor acts as:
DC series motor
DC shunt motor
DC series generator
DC shunt generator
Which of the following motors is suitable for high starting torque?
shunt motor
cumulative compound motor
series motor
compound motor
It is preferable to start a DC series motor with some mechanical load on it because: a. it will not un at no load
it acts as starter to the motor
it may develop excessive speed and damage itself
none of these
If the flux of a DC motor approaches zero, its speed will approach:
infinity
zero
a stable value nearer to the speed
none of these
As the load is increased, the speed of a shunt motor:
remains constant c. reduces slightly
increases slightly d. none of these
The main function of a commutator in DC motor is to:
prevent sparking c. reduce friction
convert AC to DC d. convert DC to AC
A 60 Hz frequency would cause an electric light to:
turn on and off 120 times per second
flicker noticeable
turn on and off 180 ties per second
turn on and off 60 times per second
The greatest value attained during one half of the cycle is called the:
peak value c. RMS value
average value d. effective value
The RMS value of a sine wave is equal to:
0.637 max value c. 0.506 max value
0.707 max value d. 1.414 max value
Form factor is defined as:
RMS value/peak value
max value/ RMS value
RMS value/average value
effective value/ RMS value
The value form factor for pure sine wave is:
1.414 c. 0.637
0.707 d. 1.110
The value of peak factor for a pure sine wave is:
1.414 c. 0.637
0.707 d. 1.110
If the current and voltage are out of phase by 90°, the power is:
1.10 Vl c. minimum
maximum d. zero
RMS value and the mean value is the same in case of:
square wave
sine wave
triangular wave
half wave rectified sine wave
The form factor of DC supply voltage is always:
infinite c. 0.5
Zero d. unity
When the sole purpose of an alternating current is to product heat, the selection of conductor is based on:
average value of current c. RMS value of current
peak value of current d. any of the above
In the impedance triangle, the inductive reactance and impedance phasor are analogous to the _______ and _____ phasor respectively in the voltage triangle: a. inductive voltage, total voltage
inductive current, total current
inductive voltage, resistive voltage
inductive current, resistive current
The phase angle of a series RL circuit is the angle between the ______ phasor and the ______ phasor: a. resistance, inductive reactance
resistance, impedance
inductive reactance, impedance
none of these
Fr an RL circuit, the power factor cannot be less than _____ or greater than _______: a. 0, 1
1, 0
0, -1
–1, 0
If the resistance in a series RC circuit is increased the magnitude of the phase angle: a. increases
remains the same
decreases
change in an indeterminate manner
The resistance phasor for a series RC circuit points to the right. The capacitive reactance phasor points _______ while the diagonal of the rectangle having there two phasors as sides represent the _______: a. up, impedance
down, impedance
left, current
up, total voltage
There will ________ be a frequency, called the ______ frequency, at which _________: a. sometimes, natural; XL – XC
always, natural; R = 0
always, resonant; XL = XC
sometimes, resonant; R = 0
In an RLC circuit, the impedance at resonance is:
maximum c. infinity
minimum d. zero
At a frequency less than the resonant frequency:
series circuit is capacitive and parallel circuit is inductive
series circuit is inductive and parallel circuit is capacitive
both circuits are inductive
both circuits are capacitive
The value of current at resonance in a series RLC cicuit by the value of:
R c. L
C d. all of these
In resonant circuits, the power-factor at resonance is:
zero c. 0.50
1 d. 0.707
Which of the following statements is true for a series RLC circuit tuned at resonant frequency?
the voltage across C> applied voltage
the voltage across L> applied voltage
the voltage across L and C> the applied voltage
the voltage across both L and C< the applied voltage
The current flowing in L and C at parallel resonance are:
zero c. infinite
equal d. different
A coil with large distributed capacitance has a:
low resistance
low o
low resonant frequency
high resonant frequency
The transient current is due to:
voltage applied to circuit
resistance of the circuit
impedance of the circuit
changes in stores energy is inductive and apacitance
To a highly inductive circuit, a small capacitance is added in series. The angle between voltage and current will:
increase c. remain nearly the same
decrease d. become indeterminate
In a balanced three phase star connected circuit the line voltage are equal:
to the line current
to the phase voltage
and so are the line current
but the line currents are equal
The type of AC distribution system commonly used to supply both light and power is the: a. open delta system
three phase delta system
three phase star system with neutral wire
three phase star system without neutral wire
In a balanced three phase star connected system the line voltage is:
the phasor difference of the two phase voltages
the phasor sum of the two phase voltages
0.707 times the phase voltage
1.414 times the phase voltage
The advantages of star connections over delta connections for same phase voltage is that it gives:
step down current c. extra step up current
extra step up voltage d. extra step up power
Power in a three phase delta system with balanced load is equal to:
3 x VL x lL x power factor
3 x VPH x lPH x power factor
3 x VPH x lL x power factor
3 x VL x lL x power factor
Power in star connected system is:
equal to that of delta system
2 times the delta system
3 times the delta system
3 times of a delta system
What is the minimum number of wattmeters required for measuring power of a three phase balanced load?
two c. one
four d. three
What is the minimum number of wattmeters required to measure unbalanced power for a three phase system?
two c. three
four d. one
In a 2-wattmeter method, the reading of one of the wattmeters will be zero when: a. power factor is unity
power factor is 0.50
load in one of the phase is zero
a neutral wire is not provided
For a three phase will be in proportional to the load:
the power factor of each phase will be in proportional to the load
the power factor of each phase will be the same
the power factor of at least one of the phase must be leading
the power factor of each phase maybe different
In a pure reactive circuit, the power factor is:
lagging c. leading
zero d. unity
The capacitor of power factor correction are rated in terms of:
Voltage c. KW
VA d. KVAR
In an AC circuit, a low value of reactive volt ampere compared with watts indicates:
high power factor c. leading power factor
unity power factor d. none of the above
For a parallel circuit consisting of resistance the value of power factor is the ratio of: a. impedance to reactance
reactance to impedance
resistance to impedance
impedance to resistance
For the same load, if the power factor of load is reduced, it will draw:
more current
less current
same current but less power
less current but more power
One of the reasons for improving the power factor is:
to increase the reactive power
to decrease the reactive power
to increase the real power
none of the above
The advantage of using static capacitor to improve the power factor is because they: a. are not variable
are almost loss free
provide continuous change of power factor
none of the above
An ideal current source has zero:
voltage on no load c. internal conductance
internal resistance d. none of the above
A passive network has:
no source of emf
no source of current
neither source of current nor source of emf
none of the above
Which of the following statement is not correct?
voltage source is an active element
current source is a passive element
resistance is a passive element
conductance is a passive element
A closed path made of several branches of the network is known as:
loop c. branch
junction d. none of the above
Which of the following is not non-linear element?
diode
transistor
heater coil
electric arc with unlike electrodes
For open circuited condition of Thevenin s theorem, all sources of emf in the network are replaced by: a. their internal impedance
their internal resistance
as total a big source of emf
none of the above
Open circuit voltage is the pd between two when the impedance between these points is:
infinity c. zero
reactive d. capacitive
In order to find Z in Thevenin s theorem:
all independent voltage and current sources are short circuited
circuited all independent voltage sources are short circuited and all independent current sources are open
all independent current sources are short circuited and independent voltage sources are open circuited
all independent voltage sources are open circuited and all independent current sources are open circuited
Reciprocity theorem is valid for:
active network only
passive network only
active and passive network only
none of the above
The superposition theorem is applicable to:
linear responses only
linear and non-linear impedance
linear, non-linear and time variant response
none of the above
Which of the following theorems enable a number of voltage (or current) source to be combined directly into a single voltage (or current) source?
Compensation theorem c. Superposition theorem
Reciprocity theorem d. Millman's theorem
In compensation theorem a network containing generator can be replaced by:
its zero internal resistance
its infinite resistance
another generator
LC circuit
Norton s theorem reduces a two terminal network to:
a constant voltage source and an impedance in parallel
a constant voltage source and an impedance in series
a constant current source and an impedance in parallel
a constant current source and an impedance in series
For maximum power transfer, according to maximum power transfer theorem, source impedance:
must be very much large as compared to the load impedance
must be complex conjugate of load impedance
must be equal to load impedance
must be very small as compared to the load impedance
The principle of working of a transformer is:
static induction c. mutual induction
dynamic induction d. self induction
Transformer is used to change the value of:
frequency c. power
voltage d. power factor
The laminations are made from:
low carbon steel
silicon steel sheet
nickel alloy steel stampings
chrome steel sheets
What is common in the two windings of a transformer:
electric circuit c. winding wire gauge
magnetic circuit d. none of these
Preferably, the resistance between the primary and the secondary of a transformer should be: a. as low as possible
as high as possible
low or high depending upon whether it is step up or sep down
high or low depending upon whether it is step up or step down
Ideal transformer assumptions do not include:
zero reactance of windings
zero resistance of windings
no leakage flux
no saturation of core
The reactance of a transformer is determined by its:
leakage flux
common core flux
size of the core
permeability of the material of the core
The resistance of low voltage side of a transformer:
is equal to resistance of its high voltage side
is more than resistance of its high voltage side
is less than the resistance of its high voltage side
(b) or (c)
The basic property of the transformer is that it changes the voltage level of an AC signal:
without changing the power
without changing its shape
without changing its frequency
without changing power, frequency or shape
At every instant the direction of secondary current in a transformer must be such as to oppose any change in flux. Th is in accordance with:
Faraday s law c. Lenz's law
Joule s law d. Coulomb s law
The magnitude of mutual flux in a transformer is:
low at low loads and high at high loads
high at low loads and low at high loads
same at all levels
varies at low loads and constant at high loads
Transformers are rated in:
kW c. k-WH
kV d. kVA
What type of core is used for a high frequency transformer?
air core c. aluminum core
closed iron core d. open iron core
The no-load current of a transformer in terms of full load current is usually:
1 to 3% c. 9 to 12%
3 to 9% d. 12 to 20%
Which of the following is a correct statement about eddy currents?
eddy currents improve the efficiency of a motor
eddy currents heat up the metal parts
eddy currents do not influence the movement
eddy currents are used for arc welding
Which of the statement given below is true about autotransformer?
it has two separate windings connected in series externally
it can only step down the voltage
it has only one winding
it is most suitable for power transformer
In any transformer, the voltage per turn in primary and secondary remains:
always different c. always in ratio of K
always same d. sometimes same
Power transformers are designed to have maximum efficiency at:
no load c. near full load
half load d. little more than full load
As compared to an amplifier a transformer cannot:
increase output power
increase the output current
increase the output voltage
none of these
Two transformers when operating in parallel will share the load depending upon their:
magnetizing current c. per unit impedance
leakage reactance d. efficiency
All day efficiency of a transformer ηA:
ηA = Electrical efficiency of transformer
ηA > Electrical efficiency of transformer
ηA < electrical efficiency of transformer
none of these may be true
No load primary output is practically equal to the iron losses in the transformer because:
primary current is small
secondary current is small
both the current are small
no load input is not equal to iron losses
If the supply frequency to the transformer is increased, the iron loss will:
decrease c. no not change
increase d. none of the above
The size of the transformer core will depend on:
frequency
flux density of the core material
area of the core
(a) and (b) both
Alternators mostly work on rotating field type principle which is different from DC machines where the field is stationary. Therefore, the alternators:
don t obey Faraday s law
work on Faraday's law
do not obey Lenz s law
don t obey Ohm s law
In huge alternators, the moving part is:
brushes c. poles
armature d. none of these
High alternators have a rotor construction
similar to DC machines c. of salient type
of non-salient type d. none of the above
The voltage applied to the field of a rotating cylindrical rotor type alternators:
high DC voltage c. low DC voltage
high AC voltage d. low AC voltage
Alternators are usually designed to generator to generate:
variable frequency c. definite frequency
definite currents d. definite power factor
The standard practice, now a days in alternators is to have:
rotating field
rotating armature
either rotating field or rotating armature
none of the above
When the speed of alternators increases, the frequency:
decreases c. increases
remains same d. changes
Distributing the armature winding of alternator in more than one number of slots per pole per phase results is:
reduction of irregularities produced in the waveform
economy of materials used in winding
less weight of the entire armature
increase of generated emf per phase
For two alternators in parallel, if the load shared by one of them is:
To be strengthened keeping input torque same
To be weakened keeping input torque same
To be kept constant but input torque should be increased
None of these
When the power factor of load is unity, the armature flux of an alternator will be:
demagnetizing c. cross magnetizing
square wave form d. none of these
An alternator is said to be over-excited if it is operating at:
leading pf c. unity pf
lagging pf d. none of these
If the input of the prime mover of an alternator is kept constant but the excitation is increased the: a. KVA will be leading
KVA will be lagging
KW will be changed
the power factor of the load remain constant
If Xs = the synchronous reactance of the machine, Xe = leakage reactance and Xa = reactance due to armature flux then:
Xa = Xs – Xe c. Xa = Xe – Xs
Xa = Xs + Xe d. Xe = XsXa
High voltage alternators are usually of the rotating field type.
This means the generated voltage is connected: a. through slip rings to the load
through slip rings to the rotating field
directly to load
directly to rotor
The maximum current that can be supplied by alternator depends upon the:
strength of the exciter voltage
number of poles
strength of the magnetic fluid
maximum heat dissipation
Synchronous impedance of an alternator is defined as the ratio of:
short circuit voltage to short circuit current
open circuit voltage to short circuit current
short circuit current to no load current
open circuit voltage to short circuit current for same value of excitation
Pitch factor is defined as the ratio of the emf s of:
distribution winding to full pitch winding
short pitch coil to full pitch coil
full pitch winding to short pitch winding
full pitch winding to concentrated winding
Synchronization of alternators means:
connecting alternators in series
transferring load from one alternator to another
connecting alternators in parallel
adjusting the excitation of the alternator
For synchronizing three phase alternator, the additional requirements is that the phase rotation:
must be the same c. is anti-clockwise
is clockwise d. none of the above
Adjustment of field excitation on one of the two alternators operating in parallel:
increase its load c. decreases its load
change its frequency d. change its power factor
If the input to the prime mover of an alternator is kept constant but the excitation is changed, then
the reactive component of the output is changed
the active component of the output is changed
the p.f. of the load remains constant
none of the above
Synchronous motor is capable of being operated at
lagging power factor only
leading power factor only
lagging and leading power factor
none of these
When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
decreases to half the original value
remains same as the original value
increases to two times the original value
tends to become zero
The maximum power developed in a synchronous motor
occurs at a coupling angle of
0° c. 90°
45° d. 180°
Synchronizing power of a synchronous machine is:
equal to synchronous reactance
inversely proportional to the synchronous reactance
directly proportional to the synchronous reactance
none of these
Synchronous motors are:
self-starting c. essentially self-starting
not self-starting d. none of these
An over-excited synchronous motor take:
lagging current
leading current
lagging and leading current
none of these
The motor in which stator and rotor magnetic field rotate at the same speed is:
induction motor c. universal motor
reduction motor d. synchronous motor
In a synchronous motor, the torque angle is:
the angle between the rotating stator flux and rotor poles
the angle between the magnetizing current and back emf
the angel between the supply voltage and the back emf
none of the above
In a synchronous motor, which loss does not vary with load?
copper losses c. windage losses
hysteresis losses d. none of the above
A three phase synchronous motor is running clockwise. In case the direction of its field current is reversed:
the motor will continue to run in the same direction
the motor will run in the reverse direction
the motor will stop
the winding of the motor will burn
The speed regulation of a three phase synchronous motor is:
5% c. 0.4%
1% d. zero
The speed of a synchronous motor:
reduce as load increases
increases as load increases
adjust itself to new equilibrium speed whenever load changes
always remains constant
When a three phase synchronous generator is supplying a zero pf lagging load the armature field effects the main field in the following way:
directly opposes it c. augment it directly
dross-magnetizes it d. none of the above
The armature current of the synchronous motor has large values of
low excitation only
high excitation only
both low and high excitation
none of the above
The type of the motor that does not have a commutator is the:
repulsion motor c. DC shunt motor
induction motor d. universal motor
The rotor speed of an induction motor is:
the same as the synchronous speed
faster than the synchronous speed
slower than the synchronous speed
determined by frequency and the number of poles
The induction motor differs from the synchronous motor is that its:
requires a DC source for its rotor
does not require a rotating magnetic field
current is induced in its rotor
current is conducted in rotor
Squirrel cage induction motor differs from the slip ring type in that it has no:
slip rings c. windings on the stator
rotor windings d. rotating part
Squirrel cage induction motor has:
zero starting torque
very small starting torque
very high starting torque
extra starting torque and it start up for rest
The frequency of the rotor current in an induction motor is given by (if f is the supply frequency, f is the rotor frequency and S is the slip)
f = Sf c. S = ff
f' = Sf d. none of the above
Improvement in the power factor in an induction motor:
decreases torque
increases the torque
increases the current
increases the torque and decreases the current due to increased impedance
In an induction motor the torque is related with the supply voltage as:
T α V½ c. T α V2
T α V d. T α 1/V2
Torque under running condition is maximum at the slip "S":
which makes rotor reactance/phase equal to rotor resistance/phase
which makes rotor reactance/phase greater than rotor resistance/phase
which makes rotor reactance/phase lesser than rotor resistance/phase
which is independent of rotor resistance
Short circuit test on the induction motor can be used to find out:
the transformation ratio of the induction motor
power scale of circle diagram
copper losses in the induction motor
all of the above
Which of the following is a correct relation for an induction motor?
actualspeedof rotor
rotorefficiency
synchronous speed
rotor copper loss = slip x rotor input
rotor input = 2 x x gross torque x synchronous speed
all of the above relations are correct
If the air gap of the induction motor is increased:
the magnetizing current will decrease
the magnetizing current will increase
the power factor will decrease
none of the above
It is advisable to avoid line starting of induction motor and use starter because:
starting torque is very high
motor takes five to seven times its full load current
it will pick up very high speed and may go out of step
it will run in reverse direction
When using any instrument for measurement or testing an electrical circuit, your _________ should be considered first:
personal safety c. surrounding
theoretical knowledge d. dress
A moving coil voltmeter has a scale which is:
linear c. exponentially decreasing
exponentially increasing d. none of the above
High AC voltages are usually measured with:
electrostatic voltmeters
voltmeter and current transformer
potential transformer and voltmeter
voltmeter and multiplier
Under normal operation, the instrument which will be at least effective in indicating than an alternator may overheat because it is overloaded as a/an:
voltmeter c. wattmeter
ammeter d. stator thermocouple
A moving coil instrument can be used to measure:
low frequency AC c. direct current
high frequency AC d. DC and AC both
Large currents in DC circuits are almost always measured with a/an:
ammeter and multiplier
millivoltmeter and shunt
millivoltmeter and multiplier
current transformer and ammeter
For measuring voltage across an electrical load, you would connect a/an:
ammeter across the load
voltmeter in series with the load
ammeter in series with the load
voltmeter across the load
Deflection of pointer of a permanent-magnet moving coil meter for fixed currents is ____ flux density I the air gap between magnetic pole shoes and coil:
directly proportional to c. independent of
inversely proportional to d. none of the above
You are required to check the pf of an electrical load. No pf meter is available. You would use: a. a wattmeter
an ammeter
a voltmeter and an ammeter
a kW-Hr meter
Which of the following sets of AC instruments may be used to find pf of a singe phase motor:
one voltmeter and one ammeter
one voltmeter and one phase rotation meter
one voltmeter and wattmeter and one ammeter
one voltmeter, one kWH meter an one ammeter
The resistance of a field coil may be correctly measured by using:
a voltmeter and an ammeter
a Schering bridge
a Kelvin double bridge
a Maxwell bridge
A moving iron meter is useful for voltage measurement at _______ frequencies:
very high c. low
high d. none of the above
The meter that is suitable for direct current only is:
moving iron type c. electrodynamic type
permanent magnet type d. hot wire type
A cross connection between two conductor cable may be located by use of a/an:
Ohmmeter c. Varley loop
Carey Foster bridge d. Kelvin bridge
A thermocouple instrument would be useful for current measurement at _______ frequencies:
high c. very low
low d. none of the above
The hot-wire ammeter:
is used only for DC circuits
is a high precision instrument
is used only for AC circuits
reads equally on DC and/or AC circuits
You have been told by your foreman to measure the resistance of some feeders. For this purpose, your would use: a. magneto test c. a bell test
b. a megger d. none of the above
When connecting wattmeters to a load circuit consuming large current, it is necessary to use:
potential transformers c. power shunts
isolating transformers d. current transformers
Which of the following instrument will be used to measure alternating current only?
moving iron voltmeter
permanent magnet type ammeter
induction type ammeter
moving iron (attraction type) ammeter
For increasing the range of DC ammeters, you would use a/an:
inductance c. shunt
capacitor d. current transformer
A DC milliammeter may be used to measure voltages:
if a high external resistance s used in series with it
when a proper shunt is sued with it
by simply connecting it across the lines
provide a high external resistance I sued across its terminals
A millimeter can be used:
as a voltmeter
only as an ammeter
both as voltmeter and ammeter
none of the above
Which of the following is commonly used for extending the range of an AC ammeter?
a current transformer c. a shunt
a capacitor d. an inductance
A shunt is used in parallel with a DC ammeter measuring large currents in order to:
reduce meter current
provide damping for meter pointer
protect meter against shorts
increase sensitivity of the ammeter
For testing and calibrating a polyphase KWH meter using a single phase supply, the best method is to connect the:
current coils in series and voltage coils in parallel
voltage coils in series and current coils in parallel
voltage coils in parallel and current coils in parallel
voltage coils in series and current in parallel
A hot wire ammeter when used to measure the output current of full wave rectifier will register _______ of the maximum value of the rectified current:
1.0 c. 0.353
0.707 d. 0.637
When operating properly, a certain circuit requires a maximum current of 10 A. Is a calibrated ammeter connected in the circuit reds 13 A, it is possible that: a. one of the branch circuits is open
a partial short exists somewhere in the circuit
the main ground connection is open
a high resistance connection exists somewhere in the circuit
A newly completed lighting equipment is always subjected to high voltage test in order to:
check the dielectric strength of the insulation
measure insulation resistance of the wiring
make sure that the equipment will be able to withstand the operating voltage
find the maximum voltage the equipment can withstand
A high voltage dielectric test performed on wires and cables is primarily meant to check:
dielectric strength of the insulation
insulation resistance
ability of the insulation to withstand the voltage it is likely to be subjected to when n service
moisture absorption quality of the insulation used
For proper connection of a single phase wattmeter to a circuit, you should use two:
current leads only
current and two potential leads
potential leads only
current leads and two power leads
Which of the following instruments usually has lowest resistance?
megger c. voltmeter
frequency meter d. ammeter
A megger is generally used to:
determine the speed of an electrical motor
measure resistance of a lightning cable
test a lighting circuit for ground
measure the amount of illumination
To measure the emf of a Weston standard cell, one would use a/an:
moving coil voltmeter c. galvanometer
electrostatic voltmeter d. potentiometer
In the two wattmeter method of 3 phase power measurement if both wattmeters read positive and equal values, then pf of the load is:
0 c. 0.5
unity d. 0.866
The ampere-hour (A-hr) is associated with:
rectifiers c. electromagnets
transformer d. storage cells
Deflection sensitivity of deflecting pates of cathode ray tube _______ the distance between deflection plates: a. is directly proportional to
is inversely proportional to
does not depend on
none of the above
If one of the two wattmeters used for measuring power taken by a balanced three phase reads zero, then pf of the load is:
0.866 lagging c. unity
0.5 d. zero
One disadvantage of using a moving iron ammeter to measure DC current is that:
its calibration gives rms value of current
it responds only to AC currents
its scale is even
its coil needs unmanageably large number of turns
Signal injection/tracing is a method commonly used in troubleshooting:
industrial wiring c. residential wiring
electric motors d. a radio
The instrument often used for checking the degree of motor shaft misalignment is:
a voltmeter c. dial indicator
a clamp on an ammeter d. megohmeter
The frequency stability of a crystal oscillator depends upon:
crystal
tuned circuit
crystal as well as the tuned circuit
all of the above
A 15 A fuse is found open and the servicer has no replacement but has a choice between 10 A and 30 A fuse. He should use:
10 A fuse c. either a and b
30 A fuse d. both a and b
The type of thermostat commonly used in appliance with heating element is:
circuit breaker c. bimetallic
magnetic relay d. thermocouple
Hay bridge is usually used for measuring:
inductance c. resistance
capacitance d. all of the above
Schering bridge is used for measurement:
inductance c. capacitance
frequency d. none of the above
The Wein s bridge is particularly useful for measuring frequencies of _____ value:
very high c. low
high d. all of the above
Impedance relay is used to protect:
line beyond a particular zone
line within a particular zone
the whole transmission system
none of the above
A current measuring instrument can be modified to measure voltages by:
using thicker wire in the coil
using a high resistance shunt
adding resistance in series
adding resistance in parallel
Buchholz relay is used in ______ protection:
generator c. line
transformer d. all of the above
Two principal parts of a permanent magnet moving coil
(PMMC)
pivots and jewel bearings c. case and iron ore
needle and scale d. coil and magnet
What is the purpose of providing a mirror behind the pointer in measuring instruments?
the scale is illuminated through the mirror
with the help of the mirror it can be seen whether the pointer is bent or not
the mirror is semi-transparent so as to allow the observation of the interior of the instrument
reading errors due to inclined observation are eliminated by removing parallax between the pointer and its image in the mirror
Meter accuracy is determined by:
half-scale deflection
full-scale deflection
one-fourth of full scale deflection
one-tenth of full scale deflection
Threshold of sensitivity with respect to instruments is:
the maximum signal which can be measured
the value of sensitivity on the highest scale
the value of sensitivity on the lowest scale
the smallest signal that result in a detectable output
On which of the following factors the sensitivity in accuracy of an instrument does not depend?
hysteresis or dead bond c. frequency response
amplitude distortion d. all of these
To increase the range of a voltmeter
a low resistance is connected in series
a low resistance is connected in parallel
a high resistance connected in series
a high resistance is connected in parallel
1021.Moving coil instruments are use
in AC circuits only c. in DC only
both AC and DC circuits d. for measuring voltage only
Which of the following damping methods is common in moving coil instruments?
air damping c. spring damping
fluid damping d. eddy-current damping
A moving iron type has
a linear scale
a nonlinear scale
its deflection is directly proportional to the current
its deflection directly proportional to the voltage
The function of a shunt in ammeter is usually
by pass the current
increase the current in the coil
decrease the voltage drop
increase the meter resistance
The shunt resistance in an ammeter is usually
less than meter resistance
equal to meter resistance
greater than mater resistance
of any value
A low voltage is measured on higher scale of voltmeter. The instrument would have
low accuracy c. low precision
low resolution d. all of these
An electrodynamic meter can be used to measure
AC voltage
DC voltage
DC as well as AC voltage
DC voltage but for AC voltages rectification is necessary
A multimeter consists of
voltmeter and ohmmeter
voltmeter and current meter
current meter and ohmmeter
voltmeter, current meter and ohmmeter
1029.Megger is an instrument to measure
very low resistance c. Q of a coil
insulation resistance d. inductance of a coil
Megger in its operation is based upon
moving coil meter c. dynamic meter
moving iron meter d. electrostatic meter
Which of the following equipment is not a part of megger
hand crank
moving coil meter
a coil of high inductance
gear box generator
Inductance is measured in terms of capacitance and
resistance by
Schering bridge c. Maxwell-Wein bridge
Anderson bridge d. Wein bridge
The potentiometer wire should have
high specific resistance and high temperature coefficient
high specific resistance and low temperature coefficient
low specific resistance and high temperature coefficient
low specific resistance and low temperature coefficient
A wattmeter can measure
AC power only
DC power only
AC as well as DC power
DC power and AC power after rectification
A relay in which the measurement is performed by a stationary circuit and which has no moving parts is known as a. static relay c. instantaneous relay
b. differential relay d. time relay
While selecting a gas for circuit breaker, the property of gas that should be considered is a. high dielectric strength
non-inflammability
non-toxicity
none of the above
1037.For high AC circuit breakers, the rated short circuit current is passed for
0.01 sec c. 3 sec
0.10 sec d. 30 sec
Which of the following is not a type of the contactor for circuit breakers?
electro-magnetic c. pneumatic
electro-pneumatic d. vacuum
There is definite objection to use of which of the following medium for extinguishing the arc in case of a circuit breaker?
air c. vacuum
SF6 gas d. water
In a circuit breaker, the active recovery voltage depends upon
power factor c. circuit condition
armature reaction d. all of the above
A relay used for protection of motors against overload is
impedance relay
electromagnetic attraction type
c. thermal relay
d. Buchholz s relay
A fuse wire should have
low specific resistance and high melting point
low specific resistance and low melting point
high specific resistance and high melting point
high specific resistance and low melting point
The number of cycles in which a high-speed circuit breaker can complete its operation is
3 to 8 c. 20 to 30
10 to 18 d. 40 to 50
A material best suited for manufacturing of fuse wire.
Aluminum c. Lead
Silver d. Copper
