2013-06-20
APTRANSCO 2012 ELECTRICAL Previous Paper APTRANSCO 2012 KEY ELECTRICAL 1. 1. A voltage waveform v(t)= 12 t2 is applied across a 1H inductor for t>=0 with initial current through it being zero. The current through the inductor for t>=0 is given by-----------(4t3) 2. Two incandescent light bulbs fo 40w and 60w rating are connected in series across the mains. Then--------(the 40 bulb glows brighter) 3. Given two coupled inductors L1 and L2, their mutual inductances M satisfies-----(M 4. Consider the star network. The resistance between terminals A and B with C open 6ohms, between terminals B and C with A open is 11ohms, and between terminals C and A with B open is 9ohms. Then ------------(Ra=2, Rb=4, Rc=7) 5. In a series RLC circuit at resonance, the magnitude of the voltage developed across the capacitor------( can be greater than the input voltage, however, it is 900 out of phase with the input voltage) 6. A two port device is defined by the following pair of quations: i1=2v1+v2 and i2=v1+v2 its impedance parameters (z11, z12, z21, z22) are-----(1,-1,-1,2) 7. The impulse response of an initially relaxed linear system is e-2tu(t).to produce a response of te-2tu(t), the input must be equal to--------(e-2t u(t)) 8. The no of roots on the equation 2s4+s3+3s2+5s+7=0 that lie in the right half of s plane is-------(2) 9. For a feedback control system of type 2, the steady state error for a ramp input is-------(zero) 10. The output of a linear time invariant control system is c(t) for a certain input r(t). if r(t) is modified by passing it through a block whose transfer function is e-s and then applied to the system, the modified output of the system would be-----------(c(t-1)u(t-1) 11. The phase lead compensation used to-----(decreases both rise time and overshoot)
12. Consider two buses connected by an impedance of (0+j5)ohm. The bus 1 voltage is 100/300 v, and bus 2 voltage is 100/00 v. the real and reactive power supplied by bus 1, resp are……….(1000w, 268 VAr) 13. For a fixed value of complex power flow in a transmission line having a sending end voltage V, the real power loss will be proportional to-----------(1/V2). 14. During a disturbance on a synchronous machine, the rotor swings from A to B before finally settling down to a steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s)--------------------(A and B) 15. A 100 MVA, 11kv, 3 phase 50hz, 8 pole synchronous generator has an inertia constant H equal to 4 MJ/MVA. The stored energy in the rotor of the generator at synchronous speed will be---(400MJ). 16. In a biased differential relay the bias is defined as a ratio of----------(operating coil current and restraining coil current)) 17. Resistance switching is normally employed in------(ABCB) 18. The use of high speed circuit breakers----(improves system stability) 19. Keeping in view the cost and overall effectiveness, the following circuit breaker is best suited for capacitor bank switching---(vacuum) 20. If the reference bus is changed in two load flow runs with the same system data and power obtained for reference bus taken as specified P and Q in the latter run----------( the system losses will be unchanged but complex bus voltages will change.) 21. The gauss seidel load flow method has following disadvantages. Tick the incorrect statement------( unreliable convergence) 22. The torque speed characteristics of a repulsion motor resembles which of the following dc motor characteristic------------(series) 23. Which type of motor is most suitable for computer printer drive-----(stepper motor) 24. A 4 pole lap wound DC generator has a developed power of P watts and voltage of E volts. Two adjacent brushes of the machine are removed as they are worn out. If the machine operates with the remaining brushes, the developed voltage and power that can be obtained from the machine are----(E,P/4)
25. A 4 point starter is used to start and control the speed of a -----------( dc shunt motor with field weakening control) 26. The function of oil in a transformer is-----( to provide insulation and cooling) 27. The core flux of a practical transformer with a resistive load------------( is strictly constant with load changes) 28. In a transformer zero voltage regulation at full load is----(possible at leading pf load) 29. A single phase transformer has a turns ratio of 1:2, and is connected to a purely resistive load. The magnetizing current drawn is 1 A, and the secondary current is 1A. if core losses and leakage reactance are neglected, the primary current is-(2.24A) 30. The low voltage winding of a 400/230V, single phase 50hz transformer is to be connected to a 25hz, the supply voltage should be-------(115V) 31. A 400/100V, 10 KVA two winding transformer is reconnected as an auto transformer is reconnected as an auto transformer across a suitable voltage source. The maximum rating of such an arrangement could be-----(50KVA) 32. When the supply voltage to an induction motor is reduced by 10%, the maximum torque will decrease by approximately-------(20%) 33. In case of a split phase motor, the phase shift between currents in the two windings is around------(300) 34. Starting torque can be obtained in the case of a single phase induction motor with identical main and auxiliary windings by connecting-----( a capacitor in series with the auxiliary winding) 35. For a single phase capacitor start induction motor which of the following statements is valid---( the direction of rotation can be changed by reversing the main winding terminals) 36. An induction motor having full load torque of 60zNm when delta connected develops a starting torque of 120Nm. For the same supply voltage, if the motor is changed to star-connection, the starting torque developed will be-------(40NM) 37. During hunting of synchronous motor –(damper bar develops torque) 38. The phase sequence of a three phase alternator will reverse if -------(the field current remains the same but the direction of
rotation is reversed) 39. The effect of stray magnetic fields on the actuating torque of a portable instrument is max when the operating filed of the instrument and the stray fields are-(parallel) 40. A current of -8+6 (sinwt+300)A is passed through three meters. They are a center zero PMMC meter, true rms meter and MI instrument. The respective reading( in A) will be----(-8,10,10) 41. R1 and R2 are the opposite arms of a wheatstone bridge as are R3 and R, the source voltage is applied across R1 and R3 under balanced conditions which one of the following is true---(R1=R2R3/R4) 42. A dc potentiometer is designed to measure up to about 2v with a slide wire of 800mm. a standard cell of emf 1.18v obtains balance at 6010mm. a test cell is seen to obtain balance at 680mm. the emf of the test cell is-(1.34v) 43. The minimum number of wattmeters required to measure3 phase 3 wire or unbalanced power is—(2) 44. A reading of 120 is obtained when a standard inductor was connected in the circuit of a Q meter and the variable capacitor is adjusted to a value of 300pF. A lossless capacitor of unknown value C, is then connected and the same reading was obtained when the variable capacitor is readjusted to a value of 200pF. The value of Cx in pF is—(100) 45. The two inputs of a CRO are fed with the two stationary periodic signals. In the X Y mode, the screen shows a figure which changes from ellipse to circle and back to ellipse with its major axis changing orientation slowly and repeatedly. The following inference can be made from this----------(there is a constant but small phase difference between the signals) 46. SCR can be turned off—( anode current should be less than holding current) 47. The no. of pn junctions in SCR-----(3) 48. TRIAC is a—(antiparallel thyristors combination) 49. GTO can be turned off-(by using a negative current pulse) 50. Which type of control is used for controlling the ac drive by using thyristors--------(integral cycle) 51. In DC choppers the output voltage can be controlled
by using FM technique varying--------( T , Toff constant) 52. In phase control rectifiers the output voltage ripple can be controlled by—‘(load inductance) 53. Which is not a current controlled device-----(MOSFET) 54. Inverter function---------(DC to AC with variable frequency) 55. In phase controlled rectifires free wheeling diode makes-(load current continuation) 56. Dielectric heating application----(wood) 57. In induction heating the following is abnormally high--------(frequency) 58. Tractive effect w.r.t driving wheel axis--------(tangential*) 59. welding transformer sets have-------------(high current, low voltage) 60. Simplify x’y’z+x’yz’+xy’z+xyz+xyz’=-------(y’z+yz’+xz) 61.
Find out y=-----------------(P+Q+R+S)
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APTRANSCO 2012 ELECTRICAL Previous Paper APTRANSCO 2012 KEY ELECTRICAL 1. 1. A voltage waveform v(t)= 12 t2 is applied across a 1H inductor for t>=0 with initial current through it being zero. The current through the inductor for t>=0 is given by-----------(4t3) 2. Two incandescent light bulbs fo 40w and 60w rating are connected in series across the mains. Then--------(the 40 bulb glows brighter) 3. Given two coupled inductors L1 and L2, their mutual inductances M satisfies-----(M 4. Consider the star network. The resistance between terminals A and B with C open 6ohms, between terminals B and C with A open is 11ohms, and between terminals C and A with B open is 9ohms. Then ------------(Ra=2, Rb=4, Rc=7) 5. In a series RLC circuit at resonance, the magnitude of the voltage developed across the capacitor------( can be greater than the input voltage, however, it is 900 out of phase with the input voltage) 6. A two port device is defined by the following pair of quations: i1=2v1+v2 and i2=v1+v2 its impedance parameters (z11, z12, z21, z22) are-----(1,-1,-1,2)
7. The impulse response of an initially relaxed linear system is e-2tu(t).to produce a response of te-2tu(t), the input must be equal to--------(e-2t u(t)) 8. The no of roots on the equation 2s4+s3+3s2+5s+7=0 that lie in the right half of s plane is-------(2) 9. For a feedback control system of type 2, the steady state error for a ramp input is-------(zero) 10. The output of a linear time invariant control system is c(t) for a certain input r(t). if r(t) is modified by passing it through a block whose transfer function is e-s and then applied to the system, the modified output of the system would be-----------(c(t-1)u(t-1) 11. The phase lead compensation used to-----(decreases both rise time and overshoot) 12. Consider two buses connected by an impedance of (0+j5)ohm. The bus 1 voltage is 100/300 v, and bus 2 voltage is 100/00 v. the real and reactive power supplied by bus 1, resp are……….(1000w, 268 VAr) 13. For a fixed value of complex power flow in a transmission line having a sending end voltage V, the real power loss will be proportional to-----------(1/V2). 14. During a disturbance on a synchronous machine, the rotor swings from A to B before finally settling down to a steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s)--------------------(A and B) 15. A 100 MVA, 11kv, 3 phase 50hz, 8 pole synchronous generator has an inertia constant H equal to 4 MJ/MVA. The stored energy in the rotor of the generator at synchronous speed will be---(400MJ). 16. In a biased differential relay the bias is defined as a ratio of----------(operating coil current and restraining coil current)) 17. Resistance switching is normally employed in------(ABCB) 18. The use of high speed circuit breakers----(improves system stability) 19. Keeping in view the cost and overall effectiveness, the following circuit breaker is best suited for capacitor bank
switching---(vacuum) 20. If the reference bus is changed in two load flow runs with the same system data and power obtained for reference bus taken as specified P and Q in the latter run----------( the system losses will be unchanged but complex bus voltages will change.) 21. The gauss seidel load flow method has following disadvantages. Tick the incorrect statement------( unreliable convergence) 22. The torque speed characteristics of a repulsion motor resembles which of the following dc motor characteristic------------(series) 23. Which type of motor is most suitable for computer printer drive-----(stepper motor) 24. A 4 pole lap wound DC generator has a developed power of P watts and voltage of E volts. Two adjacent brushes of the machine are removed as they are worn out. If the machine operates with the remaining brushes, the developed voltage and power that can be obtained from the machine are----(E,P/4) 25. A 4 point starter is used to start and control the speed of a -----------( dc shunt motor with field weakening control) 26. The function of oil in a transformer is-----( to provide insulation and cooling) 27. The core flux of a practical transformer with a resistive load------------( is strictly constant with load changes) 28. In a transformer zero voltage regulation at full load is----(possible at leading pf load) 29. A single phase transformer has a turns ratio of 1:2, and is connected to a purely resistive load. The magnetizing current drawn is 1 A, and the secondary current is 1A. if core losses and leakage reactance are neglected, the primary current is-(2.24A) 30. The low voltage winding of a 400/230V, single phase 50hz transformer is to be connected to a 25hz, the supply voltage should be-------(115V) 31. A 400/100V, 10 KVA two winding transformer is reconnected as an auto transformer is reconnected as an auto transformer across a suitable voltage source. The maximum rating of such an arrangement could be-----(50KVA)
32. When the supply voltage to an induction motor is reduced by 10%, the maximum torque will decrease by approximately-------(20%) 33. In case of a split phase motor, the phase shift between currents in the two windings is around------(300) 34. Starting torque can be obtained in the case of a single phase induction motor with identical main and auxiliary windings by connecting-----( a capacitor in series with the auxiliary winding) 35. For a single phase capacitor start induction motor which of the following statements is valid---( the direction of rotation can be changed by reversing the main winding terminals) 36. An induction motor having full load torque of 60zNm when delta connected develops a starting torque of 120Nm. For the same supply voltage, if the motor is changed to star-connection, the starting torque developed will be-------(40NM) 37. During hunting of synchronous motor –(damper bar develops torque) 38. The phase sequence of a three phase alternator will reverse if -------(the field current remains the same but the direction of rotation is reversed) 39. The effect of stray magnetic fields on the actuating torque of a portable instrument is max when the operating filed of the instrument and the stray fields are-(parallel) 40. A current of -8+6 (sinwt+300)A is passed through three meters. They are a center zero PMMC meter, true rms meter and MI instrument. The respective reading( in A) will be----(-8,10,10) 41. R1 and R2 are the opposite arms of a wheatstone bridge as are R3 and R, the source voltage is applied across R1 and R3 under balanced conditions which one of the following is true---(R1=R2R3/R4) 42. A dc potentiometer is designed to measure up to about 2v with a slide wire of 800mm. a standard cell of emf 1.18v obtains balance at 6010mm. a test cell is seen to obtain balance at 680mm. the emf of the test cell is-(1.34v) 43. The minimum number of wattmeters required to measure3 phase 3 wire or unbalanced power is—(2) 44. A reading of 120 is obtained when a standard
inductor was connected in the circuit of a Q meter and the variable capacitor is adjusted to a value of 300pF. A lossless capacitor of unknown value C, is then connected and the same reading was obtained when the variable capacitor is readjusted to a value of 200pF. The value of Cx in pF is—(100) 45. The two inputs of a CRO are fed with the two stationary periodic signals. In the X Y mode, the screen shows a figure which changes from ellipse to circle and back to ellipse with its major axis changing orientation slowly and repeatedly. The following inference can be made from this----------(there is a constant but small phase difference between the signals) 46. SCR can be turned off—( anode current should be less than holding current) 47. The no. of pn junctions in SCR-----(3) 48. TRIAC is a—(antiparallel thyristors combination) 49. GTO can be turned off-(by using a negative current pulse) 50. Which type of control is used for controlling the ac drive by using thyristors--------(integral cycle) 51. In DC choppers the output voltage can be controlled by using FM technique varying--------( T , Toff constant) 52. In phase control rectifiers the output voltage ripple can be controlled by—‘(load inductance) 53. Which is not a current controlled device-----(MOSFET) 54. Inverter function---------(DC to AC with variable frequency) 55. In phase controlled rectifires free wheeling diode makes-(load current continuation) 56. Dielectric heating application----(wood) 57. In induction heating the following is abnormally high--------(frequency) 58. Tractive effect w.r.t driving wheel axis--------(tangential*) 59. welding transformer sets have-------------(high
current, low voltage) 60. Simplify x’y’z+x’yz’+xy’z+xyz+xyz’=-------(y’z+yz’+xz) 61.
Find out y=-----------------(P+Q+R+S)
OTHER PAPERS AP TRANSCO ELECTRICAL - TECHNICAL PAPER SUB-ENGINEERS TECHNICAL PAPER 2012 ENGINEERS TECHNICAL PAPER 2012 ELECTRICAL PAPER -SOME IMPORTANT QUESTIONS AP GENCO TECHNICAL PAPER TECHNICAL PAPER 2012 TECHNICAL PAPER 2011 AP CPDCL ELECTRICAL - TECHNICAL PAPER TECHNICAL PAPER 2010 BHEL ELECTRICAL - - TECHNICAL PAPER TEHNICAL PAPER 2010 TEHNICAL PAPER 2009
1. In a dc shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed ” ω” and armature current “Ia„” will be (A) Both ω and Iaare doubled. (B) ω is constant and Ia is doubled (C) w is doubled while Ia is halved (D) w is constant but Ia is halved Ans: B
2.The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes. Ans: C
3.A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor. Ans: C
4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz.
(C) 2 Hz. (D) Zero. Ans: C
5.The size of a conductor used in power cables depends on the (A) operating voltage.
(B) power factor.
(C) current to be carried.
(D) type of insulation
used. Ans: C
6. The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor. Ans: B
7.A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%.
(B) less than 4.5%.
4.5%.
(C) more than
(D) 4.5% or more than 4.5%.Ans: C
8 When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque. Ans: D
9 If a transformer primary is energised from a square wave voltage source, its output voltage will be (A) A square wave. (B) A sine wave. (C) A triangular wave. (D) A pulse wave. Ans: A
10 In a d.c. series motor the electromagnetic torque developed is proportional to (A) Ia (B) (Ia)2 (C) 1/Ia (D) 1/(Ia)2 Ans: B
11.The two windings of a transformer is (A) conductively linked. (B) inductively linked. (C) not linked at all. (D) electrically linked. Ans : B
12.In a 3 – phase induction motor running at slip „s‟ the mechanical power developed in terms of air gap power (A) (s-1)Pg ( B) Pg/(1-s) (C) (1-s)Pg
(D) s.Pg Ans: C
13. In a 3 – phase induction motor the maximum torque (A) is proportional to rotor resistance r2 (B) does not depend on r2 (C) is proportional to sqrt(r2) (D) is proportional to (r2)2 Ans: B
13 In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes. Ans: C
14 In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. (D) zero p.f. leading. Ans: B
15. A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed.
(C) continue to run at a speed slightly more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed. Ans: B
16.The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of (A) 900,900 (B) <900,900 (C) 900,>900 (D) 900,<900 Ans: D
17. A stepper motor is (A) a dc motor. phase motor.
(B) a single-phase ac motor.
(C) a multi-
(D) a two phase motor.
Ans: D
18.The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be (A) 3.6 V. (B) 2.5 V. (C) 3.0 V. (D) 6.0 V. Ans: C
19.In a stepper motor the angular displacement (A) can be precisely controlled.
(B) it cannot be readily interfaced with micro computer based controller. (C) the angular displacement cannot be precisely controlled. (D) it cannot be used for positioning of work tables and tools in NC machines. Ans: A
20.The emf induced in the primary of a transformer (A) is in phase with the flux. (B) lags behind the flux by 90 degree. (C) leads the flux by 90 degree. (D) is in phase opposition to that of flux. Ans: C
21.The d.c. series motor should always be started with load because (A) at no load, it will rotate at dangerously high speed. (B) it will fail to start. (C) it will not develop high starting torque. (D) all are true. Ans: A
22.The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine. Ans: all options are correct
23.The power factor of a squirrel cage induction motor is (A) low at light load only.
(B) low at heavy load only. (C) low at light and heavy load both. (D) low at rated load only. Ans: A
24. A hysteresis motor (A) is not a self-starting motor. (B) is a constant speed motor. (C) needs dc excitation. (D) can not be run in reverse speed. Ans: B
25.Out of the following methods of heating the one which is independent of supply frequency is (A) electric arc heating resistance heating
(B) induction heating
(C) electric
(D) dielectric heating
Ans: C 26. A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (A) 1500 r.p.m. (B) 1425 r.p.m. (C) 25 r.p.m. (D) 75 r.p.m. Ans: D
27.An alternator is delivering rated current at rated voltage and 0.8 powerfactor lagging case. If it is required to deliver rated current at rated voltage and
0.8 power-factor leading, the required excitation will be (A) less. (B) more. (C) more or less. (D) the same. Ans: B
28.The generation voltage is usually (A) between 11 KV and 33 KV. (B) between 132 KV and 400 KV. (C) between 400 KV and 700 KV. (D) None of the above. Ans: A
29. A ceiling fan uses (A) split-phase motor. (B) capacitor start and capacitor run motor. (C) universal motor. (D) capacitor start motor. Ans: D
Electrical Circuits and Networks:
1. The ratio of voltage and electric current in a closed circuit (a) remains constant (b) varies (c) increases (d) falls 2. The resistance of a wire varies inversely as (a) area of cross section (b) length (c) resistivity (d) temperature 3. The electrical conductivity of metals is typically of the order of ( in ohm-1 m-1) (a) 10 to the power of 7 (b) 10 to the power of 5 (c) 10 to the power of -4 (d) 10 to the power of -6 4. Four resistors, each of resistance R ohms are available. The minimum resistance of the combination will be (a) 4R (b) R (c) R/4 (d) R/8 5. The elements which are not capable of delivering energy by its own are known as (a) unilateral elements (b) non-linear elements (c) passive elements (d) active elements 6. The magentic susceptibility of paramagnetic material is (a) less than zero (b) less than one but positive (c) greater than one (d) equal to zero 7. The Direction of current in an ac circuit (a) is from positive to negative (b) is always in one direction (c) varies from instant to instant (d)Cannot be determined 8. which of the following statements associated with purely resistive circuits is correct? (a) PF is unity (b) Power consumed is zero (c) Heat produced is zero (d) PF is zero 9. The magnetic field energy in an inductor changes from maximum value to minimum value in in 5m sec when connected to an ac source. The frequency of the source is (a) 20 Hz (b) 50 Hz (c) 200 Hz (d) 500 Hz 10.
Control Systems:
1. Electronic control systems have the serious draw-backs of (a) low reliability (b) operational difficulty (c) temperature sensitiveness (d) all of above
2. The system whose characteristic equation has the following roots is marginally stable (a) -j, j, -1,1 (b) -3,-2,0 (c) -2+3j, -2-3j, -2 (d) -3,-2,-1 3. A phase log compensation will (a) improve relative stability (b)increase the speed of response (c)increase band-width (d) increase overshoot 4. For Nyquist plot we use a. open loop function b. closed loop function c. characteristic equation d. any of the above
A system with gain margin close to unity or a phase margin close to zero is
a. highly stable b. oscillatory c. relatively stable d. none of these
Root locus diagram exhibits the
a. frequency response of a system b. poles of the transfer function for a set of parameter values c. bandwidth of system d. all of the above
Increase in the gain K makes the system
a. more stable b. unstable c. none of above
The transfer function of a system is used to determine
a. the output for a given input b. the type of system
c. the input for a given output d. the steady state gain
In a servo system the voltage induced in the control transformer rotor is the
a. error voltage b. driving voltage c. opposing voltage d. none of these
With the feedback system, the transient response
a. decays slowly b. decays rapidly c. rises slowly d. rises quickly
Measurements and Instrumentation
1. Which of the following types of instrument is an integrating instrument? a. power factor meter b. energy meter c. wattmeter d. frequent meter
Which of the material is used for the ‟swamping‟ resistance that is connected in series with the working coil of a voltmeter?
a. Constantan b. Manganin c. Eureka d. Nichrome
What are used to increase the range of ammeters.
a. Multipliers b. Shunts c. Control Springs d. Potential transformers
Which voltmeter do you select for measuring 50KV DC?
a. Moving Coil Voltmeter b. Hot wire voltmeter c. Electro Dynamo meter d. Electrostatic Voltmeter
Which of the following you will prefer to extend the range of an ac voltmeter?
a. Low series resistance b. high resistance in parallel c. CT d. PT
High AC voltages are usually measured with
a. magnetic voltmeter b. inductive voltmeter c. potential transformers with voltmeters d. current transformers and voltmeters
Creeping is the phenomena occurs in
a. voltmeter b. wattmeter c. energy meter d. ammeter
APGENCO AE Hall Tickets 2012 Download Click Here new Q.1 The two windings of a transformer is (A) conductively linked. (B) inductively linked. (C) not linked at all. (D) electrically linked. Ans : B Q.2 A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed. (C) continue to run at a speed slightly more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed. Ans: B Q.3 The d.c. series motor should always be started with load because (A) at no load, it will rotate at dangerously high speed. (B) it will fail to start. (C) it will not develop high starting torque. (D) all are true. Ans: A Q.4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz. (C) 2 Hz. (D) Zero. Ans: C Q.5 In a stepper motor the angular displacement (A) can be precisely controlled. (B) it cannot be readily interfaced with micro computer based controller. (C) the angular displacement cannot be precisely controlled. (D) it cannot be used for positioning of work tables and tools in NC machines. Ans: A Q.6 The power factor of a squirrel cage induction motor is (A) low at light load only. (B) low at heavy load only.
(C) low at light and heavy load both. (D) low at rated load only. Ans: A Q.7 The generation voltage is usually (A) between 11 KV and 33 KV. (B) between 132 KV and 400 KV. (C) between 400 KV and 700 KV. (D) None of the above. Ans: A Q.8 When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque. Ans: D Q.9 If a transformer primary is energised from a square wave voltage source, its output voltage will be (A) A square wave. (B) A sine wave. (C) A triangular wave. (D) A pulse wave. Ans: A Q.10 In a d.c. series motor the electromagnetic torque developed is proportional to (A) Ia (B) (Ia)2 (C) 1/Ia (D) 1/(Ia)2 Ans: B Q.11 In a 3 – phase induction motor running at slip „s‟ the mechanical power developed in terms of air gap power (A) (s-1)Pg ( B) Pg/(1-s) (C) (1-s)Pg (D) s.Pg Ans: C
Q.12 In a 3 – phase induction motor the maximum torque (A) is proportional to rotor resistance r2 (B) does not depend on r2 (C) is proportional to sqrt(r2) (D) is proportional to (r2)2 Ans: B Q.13 In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes. Ans: C Q.14 In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. (D) zero p.f. leading. Ans: B Q.15 The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of (A) 900,900 (B) <900,900 (C) 900,>900 (D) 900,<900 Ans: D Q.16 The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be (A) 3.6 V. (B) 2.5 V. (C) 3.0 V. (D) 6.0 V. Ans: C Q.17 The emf induced in the primary of a transformer (A) is in phase with the flux. (B) lags behind the flux by 90 degree. (C) leads the flux by 90 degree. (D) is in phase opposition to that of flux. Ans: C
Q.18 The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine. Ans: all options are correct Q.19 The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes. Ans: C Q.20 A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor. Ans: C Q.21 A hysteresis motor (A) is not a self-starting motor. (B) is a constant speed motor. (C) needs dc excitation. (D) can not be run in reverse speed. Ans: B Q.22 The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor. Ans: B Q.23 The size of a conductor used in power cables depends on the (A) operating voltage. (B) power factor. (C) current to be carried. (D) type of insulation used.Ans: CQ.24 Out of the following methods of heating the one which is independent of supply frequency is (A) electric arc heating (B) induction heating
(C) electric resistance heating
(D) dielectric heating
Ans: C Q.25 A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%. (C) more than 4.5%.
(B) less than 4.5%. (D) 4.5% or more than 4.5%.
Ans: C Q.26 In a dc shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed ” ω” and armature current “Ia„” will be (A) Both ω and Ia are doubled. (B) ω is constant and Ia is doubled (C) w is doubled while Ia is halved (D) w is constant but Ia is halved Ans: B Q.27 A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (A) 1500 r.p.m. (B) 1425 r.p.m. (C) 25 r.p.m. (D) 75 r.p.m. Ans: D Q.28 An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be (A) less. (B) more. (C) more or less. (D) the same. Ans: B Q.29 A ceiling fan uses (A) split-phase motor. (B) capacitor start and capacitor run motor. (C) universal motor. (D) capacitor start motor. Ans: D
Q.30 A stepper motor is (A) a dc motor. (B) a single-phase ac motor. motor. (D) a two phase motor. Ans: D
(C) a multi-phase
Q.31 The „sheath‟ is used in cable to (A) provide strength to the cable. (B) provide proper insulation. (C) prevent the moisture from entering the cable. (D) avoid chances of rust on strands. Ans: A Q.32 The drive motor used in a mixer-grinder is a (A) dc motor. (B) induction motor. (C) synchronous motor. (D) universal motor. Ans: DQ.33 A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals(A) 0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps. Ans: A Q.34 A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be (A) 800 rpm. (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm. Ans: C Q.35 A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles of the motor are (A) 4. (B) 6. (C) 12. (D) 8. Ans: A
Answer Keys 1 B 2 C 3 A 4 D 5 B 6 D 7 A 8 A 9 B 10 D 11 D 12 B 13 A 14 C 15 B 16 C 17 C 18 D 19 B 20 C 21 D 22 C 23 A 24 A 25 D 26 C 27 D 28 D
29 B 30 C 31 C 32 A 33 A 34 B 35 B 36 A 37 A 38 C 39 A 40 D 41 D 42 C 43 A 44 C 45 A 46 C 47 B 48 C 49 A 50 A 51 B 52 C 53 D 54 A 55 C 56 B 57 A 58 A 59 B 60 D
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1. In a dc shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed ” ω” and armature current “Ia„” will be (A) Both ω and Iaare doubled. (B) ω is constant and Ia is doubled (C) w is doubled while Ia is halved (D) w is constant but Ia is halved Ans: B
2.The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes. Ans: C
3.A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor. Ans: C
4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz. (C) 2 Hz. (D) Zero. Ans: C
5.The size of a conductor used in power cables depends on the (A) operating voltage.
(B) power factor.
(C) current to be carried.
(D) type of insulation
used.
Ans: C
6. The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor. Ans: B
7.A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%.
(B) less than 4.5%.
4.5%.
(C) more than
(D) 4.5% or more than 4.5%.Ans: C
8 When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque. Ans: D
9 If a transformer primary is energised from a square wave voltage source, its output voltage will be (A) A square wave. (B) A sine wave. (C) A triangular wave. (D) A pulse wave. Ans: A
10 In a d.c. series motor the electromagnetic torque developed is proportional to (A) Ia (B) (Ia)2 (C) 1/Ia (D) 1/(Ia)2 Ans: B
11.The two windings of a transformer is (A) conductively linked. (B) inductively linked. (C) not linked at all. (D) electrically linked. Ans : B
12.In a 3 – phase induction motor running at slip „s‟ the mechanical power developed in terms of air gap power (A) (s-1)Pg ( B) Pg/(1-s) (C) (1-s)Pg (D) s.Pg Ans: C
13. In a 3 – phase induction motor the maximum torque (A) is proportional to rotor resistance r2 (B) does not depend on r2 (C) is proportional to sqrt(r2) (D) is proportional to (r2)2
Ans: B
13 In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes. Ans: C
14 In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. (D) zero p.f. leading. Ans: B
15. A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed. (C) continue to run at a speed slightly more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed. Ans: B
16.The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of (A) 900,900 (B) <900,900 (C) 900,>900
(D) 900,<900 Ans: D
17. A stepper motor is (A) a dc motor. phase motor.
(B) a single-phase ac motor.
(C) a multi-
(D) a two phase motor.
Ans: D
18.The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be (A) 3.6 V. (B) 2.5 V. (C) 3.0 V. (D) 6.0 V. Ans: C
19.In a stepper motor the angular displacement (A) can be precisely controlled. (B) it cannot be readily interfaced with micro computer based controller. (C) the angular displacement cannot be precisely controlled. (D) it cannot be used for positioning of work tables and tools in NC machines. Ans: A
20.The emf induced in the primary of a transformer (A) is in phase with the flux. (B) lags behind the flux by 90 degree. (C) leads the flux by 90 degree. (D) is in phase opposition to that of flux. Ans: C
21.The d.c. series motor should always be started with load because (A) at no load, it will rotate at dangerously high speed. (B) it will fail to start. (C) it will not develop high starting torque. (D) all are true. Ans: A
22.The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine. Ans: all options are correct
23.The power factor of a squirrel cage induction motor is (A) low at light load only. (B) low at heavy load only. (C) low at light and heavy load both. (D) low at rated load only. Ans: A
24. A hysteresis motor (A) is not a self-starting motor. (B) is a constant speed motor. (C) needs dc excitation. (D) can not be run in reverse speed. Ans: B
25.Out of the following methods of heating the one which is independent of supply frequency is (A) electric arc heating resistance heating
(B) induction heating
(C) electric
(D) dielectric heating
Ans: C 26. A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (A) 1500 r.p.m. (B) 1425 r.p.m. (C) 25 r.p.m. (D) 75 r.p.m. Ans: D
27.An alternator is delivering rated current at rated voltage and 0.8 powerfactor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be (A) less. (B) more. (C) more or less. (D) the same. Ans: B
28.The generation voltage is usually (A) between 11 KV and 33 KV. (B) between 132 KV and 400 KV. (C) between 400 KV and 700 KV.
(D) None of the above. Ans: A
29. A ceiling fan uses (A) split-phase motor. (B) capacitor start and capacitor run motor. (C) universal motor. (D) capacitor start motor. Ans: D
Electrical Circuits and Networks:
1. The ratio of voltage and electric current in a closed circuit (a) remains constant (b) varies (c) increases (d) falls 2. The resistance of a wire varies inversely as (a) area of cross section (b) length (c) resistivity (d) temperature 3. The electrical conductivity of metals is typically of the order of ( in ohm-1 m-1) (a) 10 to the power of 7 (b) 10 to the power of 5 (c) 10 to the power of -4 (d) 10 to the power of -6 4. Four resistors, each of resistance R ohms are available. The minimum resistance of the combination will be (a) 4R (b) R (c) R/4 (d) R/8 5. The elements which are not capable of delivering energy by its own are known as (a) unilateral elements (b) non-linear elements (c) passive elements (d) active elements 6. The magentic susceptibility of paramagnetic material is (a) less than zero (b) less than one but positive (c) greater than one (d) equal to zero 7. The Direction of current in an ac circuit (a) is from positive to negative (b) is always in one direction (c) varies from instant to instant (d)Cannot be determined 8. which of the following statements associated with purely resistive circuits is correct? (a) PF is unity (b) Power consumed is zero (c) Heat produced is zero (d) PF is zero 9. The magnetic field energy in an inductor changes from maximum value to minimum value in in 5m sec when connected to an ac source. The frequency of the source is (a) 20 Hz (b) 50 Hz (c) 200 Hz (d) 500 Hz 10.
Control Systems:
1. Electronic control systems have the serious draw-backs of (a) low reliability (b) operational difficulty (c) temperature sensitiveness (d) all of above
2. The system whose characteristic equation has the following roots is marginally stable (a) -j, j, -1,1 (b) -3,-2,0 (c) -2+3j, -2-3j, -2 (d) -3,-2,-1 3. A phase log compensation will (a) improve relative stability (b)increase the speed of response (c)increase band-width (d) increase overshoot 4. For Nyquist plot we use a. open loop function b. closed loop function c. characteristic equation d. any of the above
A system with gain margin close to unity or a phase margin close to zero is
a. highly stable b. oscillatory c. relatively stable d. none of these
Root locus diagram exhibits the
a. frequency response of a system b. poles of the transfer function for a set of parameter values c. bandwidth of system d. all of the above
Increase in the gain K makes the system
a. more stable b. unstable c. none of above
The transfer function of a system is used to determine
a. the output for a given input b. the type of system
c. the input for a given output d. the steady state gain
In a servo system the voltage induced in the control transformer rotor is the
a. error voltage b. driving voltage c. opposing voltage d. none of these
With the feedback system, the transient response
a. decays slowly b. decays rapidly c. rises slowly d. rises quickly
Measurements and Instrumentation
1. Which of the following types of instrument is an integrating instrument? a. power factor meter b. energy meter c. wattmeter d. frequent meter
Which of the material is used for the ‟swamping‟ resistance that is connected in series with the working coil of a voltmeter?
a. Constantan b. Manganin c. Eureka d. Nichrome
What are used to increase the range of ammeters.
a. Multipliers b. Shunts c. Control Springs d. Potential transformers
Which voltmeter do you select for measuring 50KV DC?
a. Moving Coil Voltmeter b. Hot wire voltmeter c. Electro Dynamo meter d. Electrostatic Voltmeter
Which of the following you will prefer to extend the range of an ac voltmeter?
a. Low series resistance b. high resistance in parallel c. CT d. PT
High AC voltages are usually measured with
a. magnetic voltmeter b. inductive voltmeter c. potential transformers with voltmeters d. current transformers and voltmeters
Creeping is the phenomena occurs in
a. voltmeter b. wattmeter c. energy meter d. ammeter
APGENCO AE Hall Tickets 2012 Download Click Here new Q.1 The two windings of a transformer is (A) conductively linked. (B) inductively linked. (C) not linked at all. (D) electrically linked. Ans : B Q.2 A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will (A) come to stop. (B) continue to run at synchronous speed. (C) continue to run at a speed slightly more than the synchronous speed. (D) continue to run at a speed slightly less than the synchronous speed. Ans: B Q.3 The d.c. series motor should always be started with load because (A) at no load, it will rotate at dangerously high speed. (B) it will fail to start. (C) it will not develop high starting torque. (D) all are true. Ans: A Q.4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz. (C) 2 Hz. (D) Zero. Ans: C Q.5 In a stepper motor the angular displacement (A) can be precisely controlled. (B) it cannot be readily interfaced with micro computer based controller. (C) the angular displacement cannot be precisely controlled. (D) it cannot be used for positioning of work tables and tools in NC machines. Ans: A Q.6 The power factor of a squirrel cage induction motor is (A) low at light load only. (B) low at heavy load only.
(C) low at light and heavy load both. (D) low at rated load only. Ans: A Q.7 The generation voltage is usually (A) between 11 KV and 33 KV. (B) between 132 KV and 400 KV. (C) between 400 KV and 700 KV. (D) None of the above. Ans: A Q.8 When a synchronous motor is running at synchronous speed, the damper winding produces (A) damping torque. (B) eddy current torque. (C) torque aiding the developed torque. (D) no torque. Ans: D Q.9 If a transformer primary is energised from a square wave voltage source, its output voltage will be (A) A square wave. (B) A sine wave. (C) A triangular wave. (D) A pulse wave. Ans: A Q.10 In a d.c. series motor the electromagnetic torque developed is proportional to (A) Ia (B) (Ia)2 (C) 1/Ia (D) 1/(Ia)2 Ans: B Q.11 In a 3 – phase induction motor running at slip „s‟ the mechanical power developed in terms of air gap power (A) (s-1)Pg ( B) Pg/(1-s) (C) (1-s)Pg (D) s.Pg Ans: C
Q.12 In a 3 – phase induction motor the maximum torque (A) is proportional to rotor resistance r2 (B) does not depend on r2 (C) is proportional to sqrt(r2) (D) is proportional to (r2)2 Ans: B Q.13 In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes. Ans: C Q.14 In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. (D) zero p.f. leading. Ans: B Q.15 The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of (A) 900,900 (B) <900,900 (C) 900,>900 (D) 900,<900 Ans: D Q.16 The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be (A) 3.6 V. (B) 2.5 V. (C) 3.0 V. (D) 6.0 V. Ans: C Q.17 The emf induced in the primary of a transformer (A) is in phase with the flux. (B) lags behind the flux by 90 degree. (C) leads the flux by 90 degree. (D) is in phase opposition to that of flux. Ans: C
Q.18 The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a (A) dc machine. (B) 3 phase induction machine. (C) synchronous machine. (D) single phase induction machine. Ans: all options are correct Q.19 The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes. Ans: C Q.20 A motor which can conveniently be operated at lagging as well as leading power factors is the (A) squirrel cage induction motor. (B) wound rotor induction motor. (C) synchronous motor. (D) DC shunt motor. Ans: C Q.21 A hysteresis motor (A) is not a self-starting motor. (B) is a constant speed motor. (C) needs dc excitation. (D) can not be run in reverse speed. Ans: B Q.22 The most suitable servomotor for low power applications is (A) a dc series motor. (B) a dc shunt motor. (C) an ac two-phase induction motor. (D) an ac series motor. Ans: B Q.23 The size of a conductor used in power cables depends on the (A) operating voltage. (B) power factor. (C) current to be carried. (D) type of insulation used.Ans: CQ.24 Out of the following methods of heating the one which is independent of supply frequency is (A) electric arc heating (B) induction heating
(C) electric resistance heating
(D) dielectric heating
Ans: C Q.25 A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%. (C) more than 4.5%.
(B) less than 4.5%. (D) 4.5% or more than 4.5%.
Ans: C Q.26 In a dc shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed ” ω” and armature current “Ia„” will be (A) Both ω and Ia are doubled. (B) ω is constant and Ia is doubled (C) w is doubled while Ia is halved (D) w is constant but Ia is halved Ans: B Q.27 A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is (A) 1500 r.p.m. (B) 1425 r.p.m. (C) 25 r.p.m. (D) 75 r.p.m. Ans: D Q.28 An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be (A) less. (B) more. (C) more or less. (D) the same. Ans: B Q.29 A ceiling fan uses (A) split-phase motor. (B) capacitor start and capacitor run motor. (C) universal motor. (D) capacitor start motor. Ans: D
Q.30 A stepper motor is (A) a dc motor. (B) a single-phase ac motor. motor. (D) a two phase motor. Ans: D
(C) a multi-phase
Q.31 The „sheath‟ is used in cable to (A) provide strength to the cable. (B) provide proper insulation. (C) prevent the moisture from entering the cable. (D) avoid chances of rust on strands. Ans: A Q.32 The drive motor used in a mixer-grinder is a (A) dc motor. (B) induction motor. (C) synchronous motor. (D) universal motor. Ans: DQ.33 A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals(A) 0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps. Ans: A Q.34 A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be (A) 800 rpm. (B) more than 800 rpm. (C) less than 800 rpm. (D) both higher or lower than 800 rpm. Ans: C Q.35 A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles of the motor are (A) 4. (B) 6. (C) 12. (D) 8. Ans: A
Answer Keys 1 B 2 C 3 A 4 D 5 B 6 D 7 A 8 A 9 B 10 D 11 D 12 B 13 A 14 C 15 B 16 C 17 C 18 D 19 B 20 C 21 D 22 C 23 A 24 A 25 D 26 C 27 D 28 D
29 B 30 C 31 C 32 A 33 A 34 B 35 B 36 A 37 A 38 C 39 A 40 D 41 D 42 C 43 A 44 C 45 A 46 C 47 B 48 C 49 A 50 A 51 B 52 C 53 D 54 A 55 C 56 B 57 A 58 A 59 B 60 D
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APTRANSCO 2012 KEY ELECTRICAL 1. 1. A voltage waveform v(t)= 12 t2 is applied across a 1H inductor for t>=0 with initial current through it being zero. The current through the inductor for
t>=0 is given by-----------(4t3) 2. Two incandescent light bulbs fo 40w and 60w rating are connected in series across the mains. Then--------(the 40 bulb glows brighter) 3. Given two coupled inductors L1 and L2, their mutual inductances M satisfies-----(M 4. Consider the star network. The resistance between terminals A and B with C open 6ohms, between terminals B and C with A open is 11ohms, and between terminals C and A with B open is 9ohms. Then ------------(Ra=2, Rb=4, Rc=7) 5. In a series RLC circuit at resonance, the magnitude of the voltage developed across the capacitor------( can be greater than the input voltage, however, it is 900 out of phase with the input voltage) 6. A two port device is defined by the following pair of quations: i1=2v1+v2 and i2=v1+v2 its impedance parameters (z11, z12, z21, z22) are-----(1,-1,-1,2) 7. The impulse response of an initially relaxed linear system is e-2tu(t).to produce a response of te-2tu(t), the input must be equal to--------(e-2t u(t)) 8. The no of roots on the equation 2s4+s3+3s2+5s+7=0 that lie in the right half of s plane is-------(2) 9. For a feedback control system of type 2, the steady state error for a ramp input is-------(zero) 10. The output of a linear time invariant control system is c(t) for a certain input r(t). if r(t) is modified by passing it through a block whose transfer function is e-s and then applied to the system, the modified output of the system would be-----------(c(t-1)u(t-1) 11. The phase lead compensation used to-----(decreases both rise time and overshoot) 12. Consider two buses connected by an impedance of (0+j5)ohm. The bus 1 voltage is 100/300 v, and bus 2 voltage is 100/00 v. the real and reactive power supplied by bus 1,
resp are……….(1000w, 268 VAr) 13. For a fixed value of complex power flow in a transmission line having a sending end voltage V, the real power loss will be proportional to-----------(1/V2). 14. During a disturbance on a synchronous machine, the rotor swings from A to B before finally settling down to a steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s)--------------------(A and B) 15. A 100 MVA, 11kv, 3 phase 50hz, 8 pole synchronous generator has an inertia constant H equal to 4 MJ/MVA. The stored energy in the rotor of the generator at synchronous speed will be---(400MJ). 16. In a biased differential relay the bias is defined as a ratio of----------(operating coil current and restraining coil current)) 17. Resistance switching is normally employed in------(ABCB) 18. The use of high speed circuit breakers----(improves system stability) 19. Keeping in view the cost and overall effectiveness, the following circuit breaker is best suited for capacitor bank switching---(vacuum) 20. If the reference bus is changed in two load flow runs with the same system data and power obtained for reference bus taken as specified P and Q in the latter run----------( the system losses will be unchanged but complex bus voltages will change.) 21. The gauss seidel load flow method has following disadvantages. Tick the incorrect statement------( unreliable convergence) 22. The torque speed characteristics of a repulsion motor resembles which of the following dc motor characteristic------------(series) 23. Which type of motor is most suitable for computer printer drive-----(stepper motor) 24. A 4 pole lap wound DC generator has a developed power of P watts and voltage of E volts. Two adjacent brushes of the machine are removed as they are worn out. If the machine operates with the remaining
brushes, the developed voltage and power that can be obtained from the machine are----(E,P/4) 25. A 4 point starter is used to start and control the speed of a -----------( dc shunt motor with field weakening control) 26. The function of oil in a transformer is-----( to provide insulation and cooling) 27. The core flux of a practical transformer with a resistive load------------( is strictly constant with load changes) 28. In a transformer zero voltage regulation at full load is----(possible at leading pf load) 29. A single phase transformer has a turns ratio of 1:2, and is connected to a purely resistive load. The magnetizing current drawn is 1 A, and the secondary current is 1A. if core losses and leakage reactance are neglected, the primary current is-(2.24A) 30. The low voltage winding of a 400/230V, single phase 50hz transformer is to be connected to a 25hz, the supply voltage should be-------(115V) 31. A 400/100V, 10 KVA two winding transformer is reconnected as an auto transformer is reconnected as an auto transformer across a suitable voltage source. The maximum rating of such an arrangement could be-----(50KVA) 32. When the supply voltage to an induction motor is reduced by 10%, the maximum torque will decrease by approximately-------(20%) 33. In case of a split phase motor, the phase shift between currents in the two windings is around------(300) 34. Starting torque can be obtained in the case of a single phase induction motor with identical main and auxiliary windings by connecting-----( a capacitor in series with the auxiliary winding) 35. For a single phase capacitor start induction motor which of the following statements is valid---( the direction of rotation can be changed by reversing the main winding terminals) 36. An induction motor having full load torque of 60zNm when delta connected develops a starting torque of 120Nm. For the same supply voltage, if the motor is changed to star-connection, the starting torque
developed will be-------(40NM) 37. During hunting of synchronous motor –(damper bar develops torque) 38. The phase sequence of a three phase alternator will reverse if -------(the field current remains the same but the direction of rotation is reversed) 39. The effect of stray magnetic fields on the actuating torque of a portable instrument is max when the operating filed of the instrument and the stray fields are-(parallel) 40. A current of -8+6 (sinwt+300)A is passed through three meters. They are a center zero PMMC meter, true rms meter and MI instrument. The respective reading( in A) will be----(-8,10,10) 41. R1 and R2 are the opposite arms of a wheatstone bridge as are R3 and R, the source voltage is applied across R1 and R3 under balanced conditions which one of the following is true---(R1=R2R3/R4) 42. A dc potentiometer is designed to measure up to about 2v with a slide wire of 800mm. a standard cell of emf 1.18v obtains balance at 6010mm. a test cell is seen to obtain balance at 680mm. the emf of the test cell is-(1.34v) 43. The minimum number of wattmeters required to measure3 phase 3 wire or unbalanced power is—(2) 44. A reading of 120 is obtained when a standard inductor was connected in the circuit of a Q meter and the variable capacitor is adjusted to a value of 300pF. A lossless capacitor of unknown value C, is then connected and the same reading was obtained when the variable capacitor is readjusted to a value of 200pF. The value of Cx in pF is—(100) 45. The two inputs of a CRO are fed with the two stationary periodic signals. In the X Y mode, the screen shows a figure which changes from ellipse to circle and back to ellipse with its major axis changing orientation slowly and repeatedly. The following inference can be made from this----------(there is a constant but small phase difference between the signals) 46. SCR can be turned off—( anode current should be less than holding current)
47. The no. of pn junctions in SCR-----(3) 48. TRIAC is a—(antiparallel thyristors combination) 49. GTO can be turned off-(by using a negative current pulse) 50. Which type of control is used for controlling the ac drive by using thyristors--------(integral cycle) 51. In DC choppers the output voltage can be controlled by using FM technique varying--------( T , Toff constant) 52. In phase control rectifiers the output voltage ripple can be controlled by—‘(load inductance) 53. Which is not a current controlled device-----(MOSFET) 54. Inverter function---------(DC to AC with variable frequency) 55. In phase controlled rectifires free wheeling diode makes-(load current continuation) 56. Dielectric heating application----(wood) 57. In induction heating the following is abnormally high--------(frequency) 58. Tractive effect w.r.t driving wheel axis--------(tangential*) 59. welding transformer sets have-------------(high current, low voltage) 60. Simplify x’y’z+x’yz’+xy’z+xyz+xyz’=-------(y’z+yz’+xz) 61.
Find out y=-----------------(P+Q+R+S)
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SUB-ENGINEERS TECHNICAL PAPER 2012 ENGINEERS TECHNICAL PAPER 2012 ELECTRICAL PAPER -SOME IMPORTANT QUESTIONS AP GENCO TECHNICAL PAPER
APTRANSCO SUB ENGINEERS 2012 KEY
1. The speed torque characteristics of a series motor is a/an-------------(Hyperbola) 2. In ad dc generator, if the variable loss is equal to constant loss, then efficiency is-------(Max) 3. The armature of a dc machine is laminated to reduce-----(eddy current loss) 4. The initial flux in a dc generator is provided by-----(residual magnetism) 5. For the operation of milling machine, which motor is used----( DC shunt motor) 6. In a series motor, the torque is----( proportional to square of armature current) 7. By conducting swinburn’s test on a dc machine, the following losses can be determined-----( constant losses) 8. The series motors have relatively----( High starting torque) 9. In a dc shunt motor, the torque developed is 15Nm at 10A of load current. If the load current is doubled, the new torque will be----(30Nm). 10. The internal characteristics of s dc shunt generator is a plot between---(Eg and Ia) 11. The back emf of motor at the time starting is -----------(zero) 12. At low flux densities, the flux in a dc generator varies----(Linearly with field current) 13. Three resistances of R ohms each are connected in delta. Its equivalent resistances in star connection per phase is -----(R/3 each)
14. The RMS value of a triangular wave of alternating quantity having peak value 3A is -----(sqrt 3) 15. In as series RL circuit, the voltage across the resistance is 40V and voltage across inductance is 40v. Then the total voltage across the series circuit--------(56.56V) 16. A transformer can have regulation closer to zero---( on leading pf) 17. The full load copper loss of a transformer is 1600watts. At half load, the copper loss----(400watts) 18. A 440/110, 1- phase transformer has a primary resistance of 0.03ohms and secondary resistance of 0.02ohms. its iron losses at normal input are 150 watts. The secondary current at which the maximum efficiency will occur is ------(82.80A) 19. Which of the following transformers should never have the secondary open circuited while primary is energized---------(CT) 20. An isolation transformer has primary to secondary turn’s ratio of------(1:1) 21. In a 50 KVA, 1-phase transformer, the iron loss is 500W and full load copper loss is 800W. The efficiency of the transformer at full load at 0.8 pf lagging is----(96.85%) 22. A synchronous motor can be used as a synchronous capacitor when it is---(over excited) 23. The harmonic component of the generated emf will be more in alternators with-------(Full pitch coils) 24. V-curves for a synchronous motor represent the relation between---(Ia and If) 25. The crawling in an induction motor is caused by-----(harmonics developed in the motor) 26. The ratio of starting torque to normal torque in case of a star delta starter will be---(1/3) 27. A 3-phase, 440v, 50hz induction motor has 4% slip. The frequency of rotor emf will be----(2Hz) 28. In a tuned line-----------( receiving end voltage and current are numerically equal to corresponding sending end values) 29. The max torque in an induction motor depends on------(frequency) 30. which of the following motors will have relatively high power factor--(capacitor run motor)
31. which of the following motors can be used for unity pf---(Schrage motor) 32. which of the following turbines will be used for heads from 500m to 200m--------(Francis) 33. The sudden change of pressure in penstock pipes due to sudden reaction of load is avoided using-------(surge tank) 34. Which of the following heat exchangers is used to raise the temperature of steam from normal to super saturation level------(superheater) 35. which of the following treatments for water is used to remove non carbonate hardness-----(Soda treatment) 36. The hoppers in electrostatic precipitator are generally----------in shape(pyramidal) 37. The purpose of cooling tower is---( to cool the steam in the condenser) 38. which is used to reduce the speed of the neutrons in a nuclear reactor----(moderator) 39. which of the following is a cladding material in nuclear reactor--(Magnesium) 40. In which of the following reactors, reactor control is achieved by varying moderator level ----------(CANDU) 41. A generating station has a connected load of 450MW and a maximum demand of 250MW. The units generated are 615*10^6 per annum. The load factor of the station is -----(0.281) 42. The plant capacity is determined by-------(Plant use factor) 43. A power plant has a maximum demand of 15MW. The load factor is 50% and the plant factor is 40%. The operating reserve is ----(3.75MW) 44. A transformer is rated at 66Kv/4001V, 1000KVA, 5% reactance. The short circuit MVA of the transformer when connected to infinite bus is----(20MVA) 45. The power frequency rms voltage, that appears across the breaker contacts after the transient oscillations die out and final extinction of arc that results in all the poles is called-------(recovery voltage) 46. In resistance switching, the function of shunt resistor----------(reduces the rate of rise of restriking voltage) 47. The no. of poles per phase of breaker is a function of------(Operating voltage) 48. The capacitor switching is easily done with------(vacuum CB)
49. A distance relay is inherently directional if its characteristics on R-X diagram is------( a circle that passes through origin) 50. The most efficient torque producing actuating structure in an induction relay is ---------(induction cup structure) 51. The line trap unit employed in carrier current relaying----(offers high impedance to carrier frequency signals) 52. The protection relay used for low fault settings and high operating speeds in a transformer is -----------(Harmonic restraint relay) 53. The wattmetric relay with directional characteristic is used for protection of generator against------(failure of prime mover) 54. The best suited relay for 3- zone protection scheme is ----(Mho relay) 55. The rule 77 of Indian electricity rules(1956) for over head lines gives information about----(clearance above ground of lowest conductor) 56. The stringing charts are used to calculate-----(Tension and sag at any temperature) 57. Due to proximity effect, the effective internal reactance of the conductor---(decrease) 58. The inductance of a single phase two wire transmission line per kilometer gets doubled when the----------------(distance between the wires is increased as square of the original distance) 59. a transmission line of 210km length has certain values for A,B,C and D parameters. If the length of line is made 100km then------(A increases and B decreases) 60. The surge impedance loading of the line is proportional to—(V^2) 61. Under no load conditions the current in a transmission line is due to-----( capacitance of the line) 62. For a transmission line, the no load receiving end voltage is more than the sending end voltage. This is called---------(Ferranti effect) 63. Corona loss can be reduced by the use of hollow conductor, because----( for a given cross section, the radius of the conductor is increased) 64. The non shielding method of over voltage protection is based on the principle of --------(insulation breakdown) 65. The valve elements of non linear resistance in valve type lighting arrester are made up of -----------(silicon carbide) 66. Which of the following lightning arresters, can discharge currents, between 65000 to 100000A-------(line type)
67. Which of the following is used to reduce tower footing resistance------(ground rods) 68. In substations, the breaker maintenance facility is provided in the---(main and transfer bus scheme) 69. In case of rigid bus arrangement, the size of aluminum pipe used for voltage level of 66KV----------------(65mm) 70. For low voltage applications up to 11KV, which of the following insulators is preferred-------(pin type) 71. In a 5 insulator disc, string capacitance between each unit and earth is 1/6 th of the mutual capacitance. The voltage distribution across the middle unit as % of voltage applied is------(17.1) 72. An electric train taking of constant current of 600A moves on a section of line between two substations 8km apart maintained at 575V and 590V resp. The track resistance is 0.04ohm per km both go and return. The point minimum potential along the track is at a distance from 575V substation is---(3.67Km) 73. which of the following is the most economical ac distribution system-----( ac 3 phase 3 wire) 74. for a distributor design, if the voltage rating is increased by ‘n’ times, the conductor size reduces to ----of the original(1/n2) 75. The pointer of an indicating instrument is generally made of -----------(aluminum) 76. Electrostatic instruments are used as-------------only(voltmeters) 77. In a dynamometer wattmeter, the moving coil is the----(potential coil) 78. A 50V range voltmeter has a sensitivity of 20 k-ohms/volt. The total resistance of the voltmeter is -----(1MOHM) 79. An RLC series resonant circuit has a Q of 15 and a source voltage of 50V. the voltage across the capacitor at resonance is -----(750V) 80. At parallel resonance conditions the power factor is--------(unity) 81. In AC circuit, V and I are given by: V=100sin(100t) V and I=100sin(100t+∏/3)mA. The power dissipated in the circuit is------(2.5W) 82. In the measurement of 3-phase power by two wattmeter method, the two wattmeter’s indicate equal readings if the power factor is----(unity) 83. In a parallel RLC circuit, below resonance frequency, the circuit behaves as----(inductive)
84. In a balanced 3-phase star connected system, the phase difference between line and phase voltages is—(30deg) 85. The electric heater draws 10A from a 230V line. The resistance of the heater is---(23ohm) 86. A wire has a resistance of 12ohms. It is bent in the form of an equilateral triangle. The effective resistance between any two corners of the triangle is---(8/3ohms) 87. ACSR stands for----------( Aluminum Conductor Steel Reinforced) 88. In house wiring, the total connected load per sub circuit can be--(800W) 89. Which of the following motors is used for intermittent high torque load and for rolling mills-----(DC cumulative compound wound motor) 90. In plugging of dc motors---------(connections to armature are reversed) 91. The motor enclosure used in wood working industry is---(totally enclosed fan cooled type) 92. The unit of luminous flux is---(lumens) 93. The illumination at a surface due to a source of light placed at a distance ‘d’ from the surface varies is ---(1/d^2) 94. Reduction factor is the ration of-----(MSCP/MHSCP) 95. Power factor is the highest in case of -----(incandescent lamp) 96. In carbon arc welding---(Electrode is positive with respect to work in case of dc supply) 97. Rolling electrodes are specifically used for---( seam welding) 98. In resistance furnace, the atmosphere is----------(oxidizing) 99. Which of the following motors can be used for unity power factor--------(Schrage motor) 100. The least expensive drive is------(belt drive)
