ELECS (1) (2)

October 2016 Pre-Board Examination ELECTRONICS ENGINEERING

When the current gain increases from 50 to 300 in an emitter-biased circuit, the collector current

Previous ()«

()



is zero



decreases by a factor of 6



remains almost the same



increases by a factor of 6

»Next

 Add your Comment

3 hours, 59 minutes, 49 seconds.

 Statistics



1



0

Correct



1.00 %

Eiciency

Wrong



99

Missed


The main function of interpoles is to minimize ____ between the brushes and the commutator when the dc machine is loaded.

Previous ()«



()

current



sparking



friction



»Next

wear and tear



 Statistics



1



1

Correct



1.00 %

Eiciency

Wrong



98

Missed


What is the differential equation for the current i (t) in the circuit of figure shown?

Previous ()«

 





 Add your Comment

()

»Next



Which of the following statements describes the basic operating principle of a magnetic amplifier?

Previous ()«

()

»Next



Any power amplifier will create a magnetic field which can be used to increase the gain of the power amplifier



A changing inductance can be used to control the current in a load

 

The inductance of an air-core inductor will change as the power used by the load changes

Magnetism can be increased (amplified) by changing the voltage amplitude

 Add your Comment


 Statistics



1

Correct



3

Wrong


An inverter on the clock input has which of the following effects on the D flip flop?

Previous ()«



()

»Next

The output will change on the negative-going transition of the clock pulse



The data input will change at the clock frequency



The output will change on the positive-going transition of the clock pulse



The output will change at the clock frequency



 Statistics



2

Correct



3

Wrong



2.00 %

Eiciency



95

Missed


A capacitor of 10 µF capacitance is allowed to discharge through its own leakage resistance and a fall of voltage from 120 V to 100 V is recorded in a time interval of 5 minutes by an electronic voltmeter connected in parallel. Calculate the leakage resistance of the capacitor.

Previous ()«

()



164.84 kΩ



164.84 GΩ



164.84 MΩ



164.84 Ω

 Explanation

 Add your Comment

»Next



LEDs are commonly fabricated from gallium compounds like gallium arsenide and gallium phosphide because they

Previous ()«



()

»Next

emit more light



are easily available



are cheap



emit more heat



 Statistics



3



4

Correct



3.00 %

Eiciency

Wrong



93

Missed


The current

is

Previous ()«

()

»Next



the same as



the emitter current in the common-collector connected transistor with zero base current





the collector current in the common-emitter connected transistorwith zero emitter current

the collector current in the common-emitter connected transistor with zero base current



 Statistics



3

Correct



5

Wrong



3.00 %

Eiciency



92

Missed


In the circuit shown, the input offset voltage and the input offset current are

= 4mV and

= 150 nA. Calculate the total offset voltage.

Previous ()«

()



497 mV



479 mV



749 mV

974 mV

  Explanation

»Next


The reverse saturation current in a junction diode is the current that flows when ______.

Previous ()«

()



the potential barrier is zero



only majority carrier are crossing the junction



the junction is unbiased



»Next

only minority carriers are crossing the junction



 Statistics



3

Correct



7

Wrong



3.00 %

Eiciency



90

Missed


The field-effect transistor (FET)

Previous ()«

()



has three NP-junctions



incorporates a forward-biased junction



depends on the variation of a magnetic field for its operation



»Next

depends on the variation of the depletion-layer width reverse voltage for its operation



 Statistics



3

Correct



8

Wrong



3.00 %

Eiciency



89

Missed


If P is Passivation, Q is n-well implant, R is metallization and S is source/drain diffusion, then the order in which they are carried out in a standard n-well CMOS fabrication process, is

Previous ()«

()



P-Q-R-S



R-P-S-Q



Q-S-R-P



S-R-Q-P

»Next



 Statistics



3



9

Correct



3.00 %

Eiciency

Wrong



88

Missed


For a given line voltage, four heating coils will produce maximum heat when connected ______.

Previous ()«



()

»Next

all in parallel



with two parallel pairs in series



one pair in parallel with the other two in series



all in series



 Statistics



4



9

Correct



4.00 %

E甦iciency

Wrong



87

Missed


The output of a filter drops from 10 to 5 V as the frequency is increased from 1 to 2 kHz. What is the dB change in the output voltage?

Previous ()«

()



-6 dB/octave



-3 dB/octave



-3 dB/decade



6 dB/octave

»Next



 Statistics



5



9

Correct



5.00 %

E蓟iciency

Wrong



86

Missed


The Q-point in a voltage amplifier is selected in the middle if the active region because

Previous ()«

()



the circuit then requires less number of resistor



the operating point then becomes very stable



it gives a distortion less output



»Next

it then requires a small dc voltage



 Statistics



5

Correct



10

Wrong



5.00 %

Eiciency



85

Missed


When determining the common-emitting current gain by making small changes in direct currents, the collector voltage is held constant so that

Previous ()«

()



the transistor will not burn out



the output resistance will be high



the change in collector current will be due to a change in base current.



the changes in emitting current will be due to a change in base current.

»Next



 Statistics



5



11

Correct



5.00 %

Eiciency

Wrong



84

Missed


Generally, the gain of a transistor amplifier falls at high frequencies due to the ____.

Previous ()«

()



internal capacitances of the device



coupling capacitor at the output



coupling capacitor at the input



»Next

skin effect



 Statistics



5

Correct



12

Wrong



5.00 %

Eiciency



83

Missed


In a feedback series regulator circuit, the output voltage is regulated by controlling the

Previous ()«

()



reference voltage



gain of the feedback transistor

 

»Next

voltage drop across the series pass transistor

magnitude of input voltage


3 hours, 54 minutes, 1 second.

 Statistics



5

Correct



13

Wrong



5.00 %

E礔iciency



82

Missed


The series field of a short-shunt dc generator is excited by ________ currents.

Previous ()«

()



external



shunt



load



»Next

armature



 Statistics



5

Correct



14

Wrong



5.00 %

E礔iciency



81

Missed


A 0 to 6 counter consists of 3 flip flop and a combination circuit of 2 input gate (s). The common circuit consists of

Previous ()«

()



One OR gate



One AND gate



One AND gate and one OR gate



»Next

Two AND gates



 Statistics



5



15

Correct



5.00 %

E礔iciency

Wrong



80

Missed


The input to an op-amp differentiator circuit is a sinusoidal voltage of peak value 10µV and frequency of 2 kHz. If the values of differentiating components are given as R = 40 k Ω and C = 3 µF, determine the output voltage.

Previous ()«

()



15.082(cos4000πt) µV



15.082(sin4000πt) µV



10.082(sin4000πt) µV



10.082(cos4000πt) µV

 Explanation

»Next



The number of minority carries crossing the junction of a diode depends primarily on the

Previous ()«



()

»Next

magnitude of the potential barrier



rate of thermal generation of electron-hole pairs.



magnitude if the forward-bias voltage



concentration of doping impurities



 Statistics



7

Correct



15

Wrong



7.00 %

Eiciency



78

Missed


What is the most useful ac bridge for comparing capacitances of two air capacitors?

Previous ()«

()



Wien series bridge



Wien parallel bridge



Schering bridge



»Next

De Sauty bridge



 Statistics



8

Correct



15

Wrong



8.00 %

Eiciency



77

Missed


Calculate the resistance of a 2 km length of aluminum overhead power cable if the crosssectional area of the cable is

Previous ()«

. Take the resistivity of aluminum to be

()



0.3 ohm



0.5 ohm



0.4 ohm



0.6 ohm

 Explanation


.

»Next



One advantage of a class B push-pull amplifier is _____. 1. Very small quiescent current drain 2. Maximum efficiency of 78.5 % 3. Greater efficiency than class A

Previous ()«



()

1, 2 and 3



2 and 3



1 and 2



1 and 3



»Next

 Statistics



9

Correct



16

Wrong


Match items in Group 1 with items in Group 2, most suitably.

Previous ()«

()



P – 3, Q - 4, R - 1, S – 2



P - 2, Q - 3, R - 1, S - 4



P - 2, Q - 1, R - 4, S - 3



P - 1, Q - 2, R - 4, S - 3



»Next

 Statistics



9

Correct



17

Wrong


By packing data within an 8-bit code, which of the following results are achieved?

Previous ()«

()



Storage space required decreases and processing speed increases



Storage space required increases and processing speed increases



Storage space required increases and processing speed decreases



Storage space required decreases and processing speed decreases

»Next



 Statistics



10

Correct



17

Wrong



10.00 %

E礔iciency



73

Missed


Surface-leakage current is part of the _______.

Previous ()«

()



forward current



reverse current



reverse breakdown current



forward breakdown current

»Next



 Statistics



10

Correct



18

Wrong



10.00 %

Eiciency



72

Missed


The forward bias applies to a PN-junction diode is increased from zero to higher values. Rapid increase in the current flow relatively small increase in voltage occurs _____.

Previous ()«





()

»Next

when the depletion area becomes larger than the space-charge area.

when the flow of minority carriers is sufficient to cause an avalanche breakdown



only after the forward bias exceeds the potential barrier.



immediately



 Statistics



10

Correct



19

Wrong



10.00 %

Eiciency



71

Missed


The circuit shown is an emitter-follower amplifier with voltage divider bias AC equivalent circuit. Calculate the voltage gain if

Previous ()«

()



0.989



0.889



0.978



0.998

 Explanation

»Next

 Add your Comment

3 hours, 51 minutes, 1 second.

 Statistics

11





Correct

11.00 %

E㼑iciency





19

Wrong

70

Missed

 Challenge friends... Search your friends & hit enter...

What's your message? (optional)



Previous ()«

 How others answered this?

()

»Next


In a semiconductor diode, the barrier potential offers opposition to only

Previous ()«

()



minority carriers in both regions



free electrons in the N-region

 

»Next

majority carriers in both regions

holes in the P-region



 Statistics



11

Correct



20

Wrong



11.00 %

Eiciency



69

Missed


A 100 µF capacitor is required in fabricating an electronic circuit. Such a large value of capacitance is possible if the capacitor is a/an

Previous ()«



()

»Next

Electrolytic capacitor



Ceramic capacitor



Mica capacitor



Air-gang capacitor



 Statistics



12



20

Correct



12.00 %

E蘓iciency

Wrong



68

Missed


A regulated power supply, shown in the figure, has an unregulated input (UR) of 15 volts and generates a regulated output

. If the unregulated voltage increases by 20%, then the power

dissipation across the transistor Q1

Previous ()«

()



increases by 20%



remains unchanged



increases by 50%



decreases by 20%

 Explanation

»Next

 Add your Comment


 Statistics



12

Correct

% 12.00



21

Wrong

67


Doping materials are called impurities because they

Previous ()«

()



decrease the number of charge carriers



make semiconductors less than 100 percent pure

 

»Next

alter the crystal structures of the pure semiconductors

change the chemical properties of semiconductors



 Statistics



12

Correct



22

Wrong



12.00 %

Eiciency



66

Missed


If in the case of a certain dc armature, the number of commutator segments is found either one less or more than the number of slots, the armature must be having a simplex ______ winding.

Previous ()«



()

lap



wave



frog leg



»Next

multielement



 Statistics



12



23

Correct



12.00 %

Eiciency

Wrong



65

Missed


The circuit shown in Figure 12 converts ________.

Previous ()«

()



Excess – 3 to gray code



Binary to excess – 3 code



Gray to Binary Code



BCD to binary code

»Next



 Statistics



12

Correct



24

Wrong



12.00 %

Eiciency



64

Missed


For the BJT,

in the circuit shown,

t=0, the switch is opened. At what time t

Previous ()«

. The switch is initially closed. At time leaves the active region?

()



10 ms



50 ms



100 ms



25 ms

 Explanation

»Next


In a PN-junction diode, if the junction current is zero, this means that

Previous ()«



()

»Next

the number of majority carriers crossing the junction equals the number of minority carriers crossing the junction



the potential barrier has disappeared



the number of holes diffusing from the P-region equals the number of electrons diffusing from the N-region.

there are no carriers crossing the junction

  Add your Comment


 Statistics

14

26





Correct

14.00 %





Wrong

60


The light-emitting diode (LED)

Previous ()«

()



gives a light output which increases with increase in temperature



is usually made from silicon

 

»Next

uses a reverse-biased junction

depends on the recombination of holes and electrons



 Statistics



14

Correct



27

Wrong



14.00 %

E礔iciency



59

Missed


If the base resistor is very small, the transistor will operate in the _____ region.

Previous ()«

()



breakdown



cutoff

 

»Next

saturation

active



 Statistics



14

Correct



28

Wrong



14.00 %

E礔iciency



58

Missed


The frequency of the system with which several alternators are paralleled can be increased by simultaneously _________ of all generators.

Previous ()«

()



decreasing the field excitation



decreasing the speed of prime movers



increasing the field excitation



»Next

increasing the speed of prime movers



 Statistics



14



29

Correct



14.00 %

Eiciency

Wrong



57

Missed


Match items in Group 1 with items in Group 2, most suitably. Group 1

Group 2

P. LEAD

1.Heavy doping

Q. Avalanche photo diode

2. Coherent radiation

R. Tunnel diode

3. Spontaneous emission

S. LASER

4. Current gain

Previous ()«

()



P - 3 Q - 4, R - 1, S – 2



P - 2, Q - 3, R - 1, S – 4



P - 2, Q - 1, R - 4, S – 3



P - 1, Q - 2, R - 4, S – 3


»Next


How is the output connected as shown in the figure? And choose what type of circuit is shown below.

Previous ()«

()

»Next



Any of the above could be correct, depending on the specific application involved.



It is an open-collector gate and is used to drive loads that cannot be connected directly to Vcc due to high noise levels.



It represents an active-LOW ni verter and is used in negative logic systems.



It is an open-collector gate. An external load must be connected between the output terminal and appropriate supply voltage.



In a PN-junction diode, holes diffuse from the P-region to the N-region because

Previous ()«



()

»Next

there is greater concentration of holes in the P-region as compared to N-region



they are swept across the junction by the potential difference



the free electrons in the N-region attract them



none of the above



 Statistics



16

Correct



30

Wrong



16.00 %

Eiciency



54

Missed


The DTL, TTL, ECL and CMOS family of digital ICs are compared in the following 4 columns:

What is the correct column?

Previous ()«

()



R



P



Q



S


»Next



In an 8085 microprocessor, the instruction CMP B has been executed while the content of the accumulator is less than that of register B. As a result

Previous ()«



()

»Next

Carry flag will be set but Zero flag will be reset



Both Carry flag and Zero flag will be set



Carry flag will be rest but Zero flag will be set



Both Carry flag and Zero flag will be rest



 Statistics



17



31

Correct



17.00 %

Eiciency

Wrong



52

Missed


Thyristor T shown is initially off and is triggered with a single pulse of width 10 µs. It is given that L=100/π µH and C = 100/π µF. Assuming latching and holding currents of the thyristor are both zero and the initial charge on C is zero, T conducts for ____.

Previous ()«



()

100 µs



50 µs



200 µs



10 µs

 Explanation

»Next


For an n−channel enhancement type MOSFET, if the source is connected at a higher potential than that of the bulk (i.e. V 0 > SB), the threshold voltage

Previous ()«



()

»Next

change polarity



increase



decrease



of the MOSFET will

remain unchanged



 Statistics



19



31

Correct



19.00 %

Eiciency

Wrong



50

Missed


What, if anything, can happen to a floppy disk when it is exposed to direct sunlight or excessive heat?

Previous ()«



()

»Next

It can become warped or distorted so it cannot be used



It can lose part of the data recorded on it



Nothing, it is not affected



It can become sticky, which stops the drive



 Statistics



20



31

Correct



20.00 %

Eiciency

Wrong



49

Missed


What is the impedance looking into nodes 1 and 2 in the given circuit as shown in the figure?

Previous ()«

()



100 Ω



50 Ω



10.1k Ω



5k Ω

 Explanation

»Next



 Statistics





 Challenge friends...

20

Correct

20.00 %

E琇iciency





32

Wrong

48

Missed

Search your friends & hit enter...





When a PN- junction is biased in the forward direction

Previous ()«

()



Only electrons in the N-region are injected into the P-region.



Only holes in the P-region are injected into the N-region.



Majority carriers in each region are injected into the region.



»Next

No carriers move.



 Statistics



20

Correct



33

Wrong



20.00 %

Eiciency



47

Missed


When the gate-to-source voltage

of a MOSFET with threshold voltage of 400 mV,

working in saturation is 900 mV, the drain current is observed to be 1 mA. Neglecting the channel width modulation effect and assuming that the MOSFET is operating at saturation, what is the drain current for an applied Previous ()«

of 1400 mV? ()



2.0 mA



3.5 mA



0.5 mA



4.0 mA

 Explanation


»Next


An SCR circuit operates from 300V DC supply, has series inductance of 4 µH. A resistance of 4Ω and capacitance of 0.2 µF is connected across the SCR. Calculate the safe dv/dt and di/dt ratings of SCR.

Previous ()«

()



75 A/µs; 133.76 V/µs



57 A/µs; 133.76 V/µs



57 A/µs; 137.36 V/µs



75 A/µs; 137.36 V/µs

 Explanation

»Next



 Statistics

21





Correct

21.00 %

E䥛iciency

34



Wrong

45



Missed

 Challenge friends... 



Previous ()«


()

»Next


The extremely high input impedance of a MOSFET is primarily due to the

Previous ()«

()



depletion of current carriers



absence of its channel

 

»Next

extremely small leakage current of its gate capacitor

negative gate-source voltage



 Statistics



21

Correct



35

Wrong



21.00 %

E礔iciency



44

Missed


The source if a silicon depth of

n-channel MOS transistor has an area of

. If the dopant density in the source is

, what is approximately the number

of holes in the source region with the above volume?

Previous ()«

()





100



10



0

 Explanation

and a

»Next


A transistor connected in common-base configuration has

Previous ()«

()



a low input resistance and high output resistance



a low input resistance and low output resistance



a high input resistance and low output resistance



a high input resistance and a high output resistance

»Next



 Statistics



22

Correct



36

Wrong



22.00 %

E礔iciency



42

Missed


A flux density of 1.2 T is produced in a piece of cast steel by a magnetizing force of 1250 A/m. Find the relative permeability of the steel under these conditions.

Previous ()«

()



764



745



746



754

 Explanation


»Next



The rms value of a half-wave rectified current is 10A, its value for full-wave rectification would be _____ amperes.

Previous ()«

()



20/π



14.14



20



40/π

»Next



 Statistics



23



37

Correct



23.00 %

Eiciency

Wrong



40

Missed


The oscillator circuit shown in the figure has an ideal inverting amplifier. What is its frequency of oscillation (in Hz)?

Previous ()«










()

»Next


A source of angular frequency 1 rad/sec has a source impedance consisting of 1 Ω resistance in series with 1 H inductance. The load that will obtain the maximum power transfer is

Previous ()«



()

»Next

1 Ω resistance in parallel with 1 H inductance



1 Ω resistance in series with 1 F capacitor



1 Ω resistance in parallel with 1 F capacitor



1 Ω resistance



 Statistics



23



39

Correct



23.00 %

Eiciency

Wrong



38

Missed


The sole purpose of a commutator in a dc generator is to __.

Previous ()«

()



increase output voltage



provide smoother output

 

»Next

convert the induced ac into dc

reduce sparking at brushes



 Statistics



23

Correct



40

Wrong



23.00 %

E礔iciency



37

Missed


Hay’s bridge is particularly useful for measuring _____.

Previous ()«





()

»Next

capacitance and dielectric loss

inductive impedance with large phase angle



mutual inductance



self inductance



 Statistics



23

Correct



41

Wrong



23.00 %

E礔iciency



36

Missed


Trickle charging of a storage battery helps to ____.

Previous ()«

()



increase its reserve capacity



prevent sulphation



keeps it fresh and fully charged



maintain proper electrolyte level

»Next



 Statistics



23

Correct



42

Wrong



23.00 %

Eiciency



35

Missed


Shunt generators are most suited for stable parallel operation because of their ____ voltage characteristics.

Previous ()«

()



identical



dropping



linear



rising

»Next



 Statistics



23



43

Correct



23.00 %

Eiciency

Wrong



34

Missed


With 10 V dc connected at port A in the linear nonreciprocal two-port network shown below, the following were observe: (i) 1Ωconnected at port B draws a current of 3A (ii) 2.5Ωconnected at port B draws a current of 2A With 10 V dc connected at port A, what is the current drawn by 7Ω connected at port B?

Previous ()«

()



9/7 A



1A



3/7A



5/7A

 Explanation

»Next



Sulphation in a lead-acid battery occur due to ____ charging.

Previous ()«





()

»Next

trickle

incomplete



fast



heavy



 Statistics



23

Correct



45

Wrong



23.00 %

Eiciency



32

Missed


Which is the wrong statement? The magnetizing force at the center of a circular coil varies

Previous ()«

()



directly as its radius



directly as the current



inversely as its radius



»Next

directly as the number of its turns



 Statistics



23

Correct



46

Wrong



23.00 %

Eiciency



31

Missed


There are no transients in pure resistive circuits because they

Previous ()«

()



obey Ohm’s law



offer high resistance



are linear circuits



»Next

have no stored energy



 Statistics



23

Correct



47

Wrong



23.00 %

Eiciency



30

Missed


An SCR has a di/dt = 120 A/µs and a dv/dt of 300 V/µs. It operates on a 250 V DC source with a load resistance of 10 Ω. Find the suitable values of inductance and capacitance of the snubber circuit.

Previous ()«

()



2.8 µH; 0.053 µF



2.8 µH; 0.53 µF



2.08 µH; 0.53 µF



2.08 µH; 0.053 µF

 Explanation

»Next


Choose proper substitutes for X and Y to make the following statements correct. Tunnel diode and Avalanche photodiode are operated in X bias and Y bias respectively.

Previous ()«

()



X : reverse, : reverse, Y: reverse



X : reverse, : reverse, Y: forward



X : forward, : reverse, Y: forward



X : forward, : reverse, Y: reverse

»Next



 Statistics



23



49

Correct



23.00 %

Eiciency

Wrong



28

Missed


Circuit shown is the common-base amplifier with voltage divider bias AC equivalent circuit. Calculate the input resistance if

Previous ()«

 

.

()

23.6 Ω

63.2 Ω



62.3 Ω



26.3 Ω

 Explanation

»Next



 Statistics

24





Correct

24.00 %

E謌iciency

49



Wrong

27



Missed




Previous ()«

()

»Next



After

reaches pinch-off value

in a JFET, drain current

Previous ()«

()



low



reversed



zero



becomes

»Next

saturated



 Statistics



24

Correct



50

Wrong



24.00 %

Eiciency



26

Missed


A single phase fully controlled bridge converter supplies a load drawing constant and ripple free load current, if the triggering angle is 30 degrees, what will be the input power factor?

Previous ()«

()



0.85



0.78



0.65



0.866

 Explanation


»Next


As compared to constant-current system, the constant-voltage system of charging a lead-acid cell has the advantage of ___.

Previous ()«



()

»Next

Both reducing time of charging and increasing cell capacity



increasing cell capacity



avoiding excessive gassing



reducing time of charging



 Statistics



25



51

Correct



25.00 %

Eiciency

Wrong



24

Missed


In a meter movement, shunt strips with a zero temperature coefficient are used instead of regular carbon resistance for which of the following reasons?

Previous ()«

()

»Next



Because regular carbon resistances are not able to handle the current changes



Because regular carbon resistances cause interfering magnetic fields



Because regular carbon resistances are affected by heat due to current and cause readings to vary

Because regular carbon resistances are too large to be used

  Add your Comment


 Statistics

25

52



Correct

% 25.00



Wrong

23


The collector voltage of a Class B push pull amplifier with

= 40 Volts swings down to a

minimum of 4 volts. The total power dissipation in both the transistors is 36 watts. Compute the total dc power input.

Previous ()«

()



121.67 W



128.25 W



122.85 W



125.28 W

 Explanation

»Next



In a PNP transistor with normal bias

Previous ()«

()



the collector junction has a low resistance



only majority carriers cross the collector junction



only holes cross the collector junction



»Next

the emitter-base junction is forward-biased and the collector-base junction is reversebiased



 Statistics



25

Correct



54

Wrong



25.00 %

Eiciency



21

Missed


For an n−channel enhancement type MOSFET, if the source is connected at a higher potential than that of the bulk (i.e. VSB > 0), the threshold voltage

Previous ()«

of the MOSFET will ___.

()



decrease



increase



remain unchanged



change polarity

»Next



 Statistics



25



55

Correct



25.00 %

Eiciency

Wrong



20

Missed


In a low-pass filter, the cutoff frequency is represented by the point where the output voltage is reduced to _____ percent of the input voltage.

Previous ()«

()



33.3



50



63.2



70.7

»Next



 Statistics



25



56

Correct



25.00 %

Eiciency

Wrong



19

Missed


A closed magnetic circuit of cast steel contains a 6 cm long path of cross-sectional area 1 cm^2 and a 2 cm path of cross-sectional area

. A coil of 200 turns is wound around the 6 cm

length of the circuit and a current of 0.4 A flows. Determine the flux density in the 2 cm path, if the relative permeability of the cast steel is 750. Previous ()«

()



1.31 T



1.61 T



1.41 T



1.51 T

 Explanation

»Next



 Statistics

25





Correct

25.00 %

E⠻iciency

57



Wrong

18



Missed




Previous ()«


()

»Next


The output of the 74 series of TTL gates is taken from a BJT in

Previous ()«

()



Common collector configuration



Totem pole and common collector configuration



Common base configuration



»Next

Either totem pole or open collector configuration



 Statistics



25

Correct



58

Wrong



25.00 %

Eiciency



17

Missed


The

through the base of a silicon NPN transistor is 1 + 0.1 cos

K,

mA. At 300

in the small signal model of the transistor is _____.

Previous ()«

()



25 Ω



27.5Ω



250 Ω



22.5 Ω

 Explanation

»Next


Three different Q points are shown on a load line. The upper Q point represents the ______.

Previous ()«



()

»Next

maximum current gain



cutoff point



minimum current gain



intermediate current gain



 Statistics



26

Correct



59

Wrong



26.00 %

Eiciency



15

Missed


What is the average power delivered to an impedance (4 - j3) Ω by a current 5 cos (100πt + 100) A?

Previous ()«

()



62.5 W



125 W



50 W



44.2 W

 Explanation

»Next


In a JFET, as external bias applied to the gate is increased

Previous ()«

()



channel resistance is decreased



drain current is increased

 

»Next

pinch-off voltage is reached at lower values of ID

size of depletion regions is reduced.



 Statistics



26

Correct



61

Wrong



26.00 %

Eiciency



13

Missed


Electrical contact materials used in switches, brushes, relay must possess

Previous ()«

()



low thermal conductivity and low melting point



high thermal conductivity and low melting point



high thermal conductivity and high melting point



low thermal conductivity and high melting point

»Next



 Statistics



26

Correct



62

Wrong



26.00 %

Eiciency



12

Missed


The voltage at the terminals of a battery is 52 V when no load is connected and 48.8 V when a load taking 80 A is connected. Find the internal resistance of the battery. What would be the terminal voltage when a load taking 20 A is connected?

Previous ()«

()



52.1 V



51.2V



49.5 V



45.9 V

 Explanation


»Next


Determine the reluctance of a piece of mumetal of length 150 mm and cross-sectional area 1800 mm^2 when the relative permeability is 4000. Find also the absolute permeability of the mumetal.

Previous ()«

()



16580



16850



15680



18650

 Explanation

»Next



The action of JFET in its equivalent circuit can best be represented as a

Previous ()«

()



Current controlled voltage source



Voltage controlled voltage source



Voltage controlled current source



Current controlled current source

»Next



 Statistics



28

Correct



63

Wrong



28.00 %

Eiciency



9

Missed


Diffusion of free electrons across the junction of an unbiased diode produces which of the following?

Previous ()«





()

»Next

Reverse bias

Depletion layer



Breakdown



Forward bias



 Statistics



28



64

Correct



28.00 %

E礔iciency

Wrong



8

Missed


In an intrinsic semiconductor, the number of free electrons

Previous ()«

()



is less than the number of holes



has no relation to number of holes

 

»Next

equals the number of holes

is greater than the number of holes



 Statistics



28

Correct



65

Wrong



28.00 %

E禵iciency



7

Missed


A regulated power supply, shown in the figure below, has an unregulated input (UR) of 15 volts and generates a regulated output

What is the power dissipation across the transistor

Q1?

Previous ()«



()

6.0 watts

6.0 watts





5.4 watts



4.8 watts

 Explanation

»Next



 Statistics

28



Correct



28.00 %



E

iciency

66

Wrong

6



Missed

 Challenge friends... Search your friends & hit enter...




Previous ()«


()

»Next


Choose the correct match for input resistance of various amplifier configurations shown below:

Previous ()«

()



CB -MO, CC-HI, CE-LO



CB -LO, CC-HI, CE-MO



CB- LO, CC-MO, CE-HI



CB -HI, CC-LO, CE-MO



 Statistics

»Next



28

Correct

%28.00

67



Wrong

5


A transformer designed for a low frequency will NOT be damaged when used at higher frequencies. What change within the transformer, limits transformer current to a safe value at higher frequencies?

Previous ()«

()



Increased hysteresis loss



Increased leakage flux

 

»Next

Increased inductive reactance

Increased eddy-current loss



 Statistics

28

68



Correct

%28.00



Wrong

4


The operating point of an NPN transistor amplifier should not be selected in the saturation region as

Previous ()«





()

»Next

it may require high dc collector supply.

it may drive the transistor to thermal runaway



it may cause output to be clipped in the negative half of the input signal



it may cause output to be clipped in the positive half of the input signal



 Statistics



28



69

Correct



28.00 %

E

iciency

Wrong



3

Missed


The input offset current equals the

Previous ()«

()



difference between two base-emitter voltages



average of two base currents



collector current divided by current gain



»Next

difference between two base currents



 Statistics



28

Correct



70

Wrong



28.00 %

Eiciency



2

Missed


If a 75-ohm sample of copper wire at 0ºC is heated to 30ºC, what is the approximate total resistance? (The temperature coefficient of resistance of copper at 0ºC is 0.00427).

Previous ()«

()



84.61 degrees



86.41 degrees



85.21 degrees



81.64 degrees

 Explanation


»Next


 Statistics


What best describes the circuit shown in Figure 6?

Previous ()«

()



A voltage doubler



A ring modulator



A bridge rectifier



A frequency discriminator

»Next



 Statistics



30

Correct



70

Wrong



30.00 %

Eiciency



0

Missed

ELECS (1) (2)

Recommend Documents