Sample Questions Electrical Engineering Basede on Actual Questions of UPSC IAS

Sample Questions Electrical Engineering Basede on Actual Questions of UPSC IAS
Engineering Question UPSC based on Real Question Papers
IAS Prelims Papers Free online solved Questions of Electrical Engineering


1. In India, the maximum frequency deviation in commercial FM broadcasting signals is about
(a) 5 kHz
(b) 15 kHz
(c) 75 kHz
(d) 200 kHz

Ans:-B


2. If the antenna diameter in a radar system is increased by a factor of 4, the maximum range will be increased by a factor of
(a) √2
(b) 2
(c) 4
(d) 8

Ans:-A

3. For any amplifier configuration using a BJT, the input Impedance R i is
(a) h i (l + h fe )
(b) h i / (1—h r Av)
(c) h i / (1+h r Av)
(d) h i / (1 + h fe )

Ans:-B

4. The range of numbers that can be represented in two’s complement mode with four binary digits is
(a) —15 to +15
(b) —8 to + 8
(c) —8 to +7
(d) —7 to +7

Ans:-A

5. Cycle time of a Random Access Memory is the time required between successive
(a) accesses to memory
(b) clocks
(c) delete operations
(d) Read / Write operations

Ans:-A


6. The INTEL 8080 microprocessors has a set of 91 Instructions. The op-code to Implement this Instruction set should be of at least
(a) 6 bits
(b) 4 bits
(c) 7 bits
(d) 8 bits

Ans:-C






7. Consider the following assembly language code for a simple computer having one register only:
LOAD X
ADD Y
STORE T1 STORE T2
MULT Z MULT T1
ADD T2 STORE R
Which one of the following arithmetic expressions does it evaluate?
(a) R:Z2(1+X+Y)2
(b) R:Z2(X+Y)2+(X+Y)
(c) R:=Z(X+Y)2+(X+Y)2
(d) R:=Z(X+Y)2+(X+Y)

Ans:-D


8. Consider the following statements regarding a ‘smart’ terminal:
1. It is a minimal system containing almost no memory.
2. It contains a small microcomputer or minicomputer.
3. It permits text editing.
4. It enables checking of typing errors made by operators.
Which of these statements are correct?
(a) 1, 2 and 3
(b) 1, 2 and 4
(c) 2, 3 and 4
(d) 1, 3 and 4

Ans:-C

9. The unit step response of a second order linear system with zero initial states is given by c (t) = 1 + 1.25 exp (— 6t) sin (8t — tan-1 1.333), t ≥ 0.
The damping ratio and the undamped natural frequency of oscillation of the system are respectively
(a) 0.6 and l0 rad/s
(b) 0.6 and l2.5 rad/s
(c) 0.8 and l0 rad/s
(d) 0.8 and 12.5 rad/s

Ans:-A


10. Type of a system depends on the
(a) number of its poles
(b) difference between the number of poles and zeros
(c) number of its real poles only
(d) number of poles it has at the origin

Ans:-D


11. The final value of function F(s) = 5 / s (s 2 + s + 2)
is equal to
(a) zero
(b) 2 / 5
(c) 5/2
(d) 5

Ans:-C

12. Consider the following statements:
1. P-D controller is equivalent to a high pass filter.
2. For better performance, integral action s initiated before derivative action.
3. High proportional gain is an alternative to derivative action.
4. A practical PID controller uses a high gain amplifier in the forward path.
Which of these statements are NOT correct?
(a) 1, 2 and 4
(b) 2, 3 and 4
(c) 2 and 3
(d) l and 4

Ans:-C

13. In measuring the distributed capacitance ‘C d’ of a certain coil using Q-meter, initial resonance at frequency 2 MHz is obtained by tuning the capacitance set to 430pF. If resonance at 4MHz is obtained by tuning the capacitance set to 100 pF, then the value of ‘C d’ would be
(a) 10 pF
(b) 20 pF
(c) l00 pF
(d) 200 pF

Ans:-A

14. Match List I (Measurements). with List II (Transduction principles) and Select the correct answer using the codes given below the Lists:
List I
A. rpm
B. Temperature
C. Static pressure
D. Current
List II
1. Variable resistance
2. Hall effect
3. Piezoelectric effect
4. Variable reluctance
5. Variable capacit4nce
Codes:
A B C D
(a) 4 1 5 2
(b) 1 4 5 2
(c) 2 1 3 5
(d) 4 1 2 3

Ans:-A


15. A resistance strain gauge with a gauge factor of 2 is fastened to a steel member subjected to a stress of 10.5 x 10’ kN/m2. The modulus of elasticity of steel is 2.1 x k N /m2. The change of resistance due to stress in the strain gauge is
(a) 0.1%
(b) 0.2%
(c) 1%
(d) 10%

Ans:-A


16. How many comparators are there In an ADC with 0— 5V Input and 8 bit output assuming a flash converter?
(a) 5
(b) 8
(c) 40
(d) 255

Ans:-D



17. The ratio of the electrical resistance of a material at 300 K to Its electrical resistance at 4 K is 5.
This material could be
(a) an intrinsic semiconductor
(b) an extrinsic semiconductor
(c) an insulator
(d) a conductor

Ans:-D



18. In a ferromagnetic material, the magnetic field is Increased gradually from zero. The first process which sets in the material to give net magnetization is the
(a) growth of favourable oriented domains at
the cost of other domains by reversible domain wall movement
(b) growth of favourable oriented domains at the cost of other domains by irreversible domain wall movement
(c) alignment of domain walls with the grain boundaries
(d) rotation of domains in the direction of the applied field.

Ans:-C

19. For the epitaxial growth of material M to be possible on the substrate of material N,
(a) the lattice constants of M and N must be same
(b) M and N must not react with each ‘other
(c) the coefficients of thermal expansion of M and N must be equal
(d) M must have a lower density than N

Ans:-A


20. Silicon nitride is used as the cover layer in MOS technology because it is
(a) easy to deposit
(b) resistant to oxidation
(c) an excellent barrier to alkali ions
(d) an excellent mask for gallium

Ans:-B

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1. The field winding of a 3-phase synchronous motor is short-circuited directly. If a 3-phase balanced voltage is impressed across the stator terminals, then the rotor will
(a) Rotate at. Synchronous speed
(b) Rotate at a speed slightly less than synchronous speed
(c) Rotate at a speed very near to half the synchronous speed
(d) Not rotate at all

Ans:-A

2. The positive, negative and zero sequence currents of a star connected load for phase R are given as
IR1 = (l0-j7) A
IR2 = (5+j15) A
JR9 = (5 —j8) A
The neutral current will be
(a) Zero
(b) (15 + j 24)
(c) (-15- j 24) A
(d) (15 – j 24) A

Ans:-A

3. In a synchronous machine, the electric circuits are armature circuit, field circuit and damper circuit and X d is d-axis synchronous reactance; X d is d-axis transient synchronous reactance and X’ is d-axis sub-transient synchronous reactance. If there is no damper winding, then
(a) X’d = X” d
(b) X’’ d = X d
(c) X’d = X d
(d) X d = X’d = X’d

Ans:-A
4. For a given load, the speed of shaded-pole single- phase induction motor fluctuates slightly because
(a) The speed of the magnetic field is not constant
(b) The magnitude of the magnetic field is not constant
(c) The motor operates at higher value of slips
(d) The motor is used with fluctuating load

Ans:-B


5. Two separate induction motors having 6 poles and 4 poles are cascaded 3-phase, 400 V, 60 Hz is the supply to the motors. The synchronous speeds (in rpm) of cascaded set will be
(a) 720, 1200, 1800 and 2400
(b) 600, 1000, 1500 and 3000
(c) 720, 1200, 1800 and 3600
(d) 600, 1200, 1800 and 2400

Ans:-C

6. A separately excited dc motor is fed from a phase- controlled converter. The motor exhibits poor speed regulation. This is due to the
(a) Inductive voltage drop of the converter and possible discontintious conduction
(b) Harmonics in the armature current
(c) Large inductance of the load current
(d) Poor power factor of the converter

Ans:-A

7. A drive suitable for low-speed high-power reversible application is the
(a) Synchro converter-fed ac drive
(b) Current source inverter-fed ac drive
(c) Voltage source (square wave) inverter-fed drive
(d) Induction motor fed from ac voltage supply

Ans:-C


8. The advantage of dual converter in the circulatory current mode is
(a) The low loss in the converter
(b) That it permits dynamic braking of connected motor
(c) The lower cost of the equipment
(d) Faster response

Ans:-D


9. A six-pulse non-reversible thyritorised 415 V ac converter is controlling a 440 V dc motor. If total drop in the circuit is limited to 10%, then the converter must be locked at an angle of
(a) 30°
(b) 600
(c) 450
(d) 900

Ans:-D

10. Which one of the following statements is correct in connection with Inverters?
(a) Both voltage source inverter and current source inverter require feedback diodes
(b) The current source inverter requires feedback diodes
(c) GTO’s can be used only in the current source inverters
(d) The voltage source inverter requires feedback diodes

Ans:-A

11. Consider a dc to dc converter (chopper) having a load resistance of 10 .0 and an Input voltage of 232 V. If the voltage drop across the converter during ON time is 2 V and the frequency of operation is1 kHz at a duty cycle of 0.4, then the average output voltage of the converter will be
(a) 94.0 V
(b) 92.8 V
(c) 92.0 V
(d) 90.8 V

Ans:-C


12. Match List I (device of thyristor family) with List II (characteristic) and select the correct answer using the codes given below the Lists:
List I
A. Asymmetrical thyristor
B. Amplifying gate thyristor
C. Triac
D. GTO
List II
1. Poor turn-off gain
2. Good di / dt capability
3. Poor reverse blocking capability
4. Good turn-off
Codes:
A B C D
(a) 2 4 1 3
(b) 2 4 3 1
(c) 4 2 3 1
(d) 4 2 1 3

Ans:-B

13. The dv/dt protection of an SCR is achieved by using
(a) RL circuit in series with SCR
(b) RC circuit across SCR
(c) L in series with SCR
(d) RC circuit in series with SCR

Ans:-B
14. Nominal-II model is normally used for evaluating the performance of
(a) Short line
(b) Medium line
(c) Long line
(d) Infinite line

Ans:-C

15. The A, B, C constants of a nominal T-circuit are given as
A = 0.95 / 0.5°
B = 85 / 70° ohm
C = 0.0005 / 90° ohm
If the two terminal voltages are held constants at 66 kV, then the steady-slate stability limit of the line will be
(a) 0.3312 MW
(b) 3.312 MW
(c) 33.12 MW
(d) 331.2 MW

Ans:-C
16. A feeder with reactance of 0.2p.u has a sending- end voltage of 1.2 p. u . If the reactive power supplied at the receiving end of the feeder is 0.3 p. u , the approximate voltage drop in the feeder will be
(a) 0.042 p. u.
(b) 0.052 p.u.
(c) 0.060 p.u.
(d) 0.070 p.u.

Ans:-B


17. Which one of the following matrices reveals the topology of the power system network?
(a) Bus incidence matrix
(b) Primitive impedance matrix
(c) Primitive admittance matrix
(d) Bus impedance matrix

Ans:-C

18. A fault occurring on an end-supplied transmission line is more severe from the point of view of RRRV if it is a
(a) Long line fault
(b) Short line fault
(c) Medium line fault
(d) Generator fault

Ans:-D

19. The insulation strength of EHV lines is mainly governed by
(a) Switching overvoltages
(b) Lightning overvoltages
(c) Power frequency overvoltages
(d) Dynamic overvoltages

Ans:-A


20. The coefficient of reflection for current of an open-ended line is
(a) -1
(b) 1
(c) 0.5
(d) Zero

Ans:-A


21. Which one of the following types of linear couplers is used for extremely reliable high-speed bus protection?
(a) Mutual inductors wound on non-magneic torodial cores
(b) Mutual inductors wound on magnetic torodial cores
(c) Capacitor voltage transformers
(d) Wire-wound resistors

Ans:-C
22. A relay most likely to operate undesirably on power swings is the
(a) Over-current relay
(b) Inverse definite minimum time relay
(c) Mho relay
(d) Reactance relay

Ans:-C

23. The inductance and capacitance of a line are respectively 1.0 H and 0.01 pF. If the
Instantaneous value of interrupted current is 10 A, the voltage across the breaker contacts will be
(a) 125kV
(b) 100kV
(c) 75 kV
(d) 66 kV

Ans:-B

24. Which of the following reason make HRC fuses preferable in power circuits?
1. They have inverse time characteristics.
2. They are consistent in performance
3. They can be selected for proper discrimination.
Select the correct answer by using the codes given below:
Codes:
(a) l and 2
(b) 2 and 3
(c) 1 and 3
(d) 1, 2 and 3

Ans:-C


25. For a 12-pulse operation of HVDC converters, the most troublesome set of harmonics on the ac side is
(a) 23rd and 25 th
(b) 12th and 24th
(c) ll th and l3th
(d) 5th and 7th

Ans:-D

electrical engineering objective questions

electrical engineering objective questions
Electrical Engineering Questions and Answers
multiple choice questions in electrical engineering

1. A shunt motor is running at its rated speed on rated load. If the field circuit gets suddenly opened
(a) Torque developed by the motor will be almost zero and the motor will stop without causing any damage to the motor
(b) The motor will draw very high armature current but it will continue to drive the load at a reduced speed.
(c) The motor would tend to race to a high speed while driving the load
(d) The motor would draw very high armature current and will stall with consequent damage to the armature

Ans:-B
2. A single-phase alternator has a synchronous reactance of 2 ohms and negligible resistance. If it supplies 10 A to a purely capacitive load at 200 V, then the generated emf will be.
(a) 240 volts
(b) 220 volts
(c) 200 volts
(d) 180 volts

Ans:-D
3. Suppose a synchronous generator connected to an infinite bus it supplying electrical power at unity PF to the bus. If its field current is now increased
(a) Both the active and reactive power output of the generator will remain unchanged
(b) The active power supplied will remain unchanged but the machine will also supply lagging reactive power
(c) The active power supplied will increase and the machine will draw leading reactive power
(d) The active power supplied will decrease and the machine will supply leading reactive power

Ans:-B



4. In the phasor-diagram of a round-rotor synchronous generator, the volt age equations is E f = V t + I e ( r a + j X a ), where E f = excitation voltage, V t = terminal voltage, Ie = armature current at lagging power factor, r a = armature resistance; Xs= synchronous reactance. While remaining synchronized to the bus-bars (infinite bus), f the power input from the prime mover is gradually decreased and finally stopped, it will result in
(a) Reversal of ‘I a’ and E lagging V t
(b) Reversal of I a but E f leading V t
(c) The sign of I a remaining unchanged, but E f leading V t
(d) The sign of I a remaining unchanged, but E f lagging V t

Ans:-C

5. A 3-phase Induction motor has a full-load slip of 3 per cent at normal voltage. Which one of the following will be the value of the slip of the motor if ft develops the same torque theoretically while operating at 110 per cent of its normal voltage?
(a) 2.48%
(b) 0.248%
(c) 0.483%
(d) 4.83%

Ans:-A


6. A 6-pole, 3-phase, 60 Hz Induction motor runs at 1000 rpm developing maximum torque. Rotor resistance per phase is 1.2 ohms. Neglecting stator impedance, then for developing maximum torque, the external resistance to be connected in series with each rotor phase will be
(a) 7.2 ohms
(b) 6 ohms
(c) 1.44 ohms
(d) 1.2 ohms

Ans:-A


7. The capacitor-start single-phase Induction motors develop much larger starting torque in comparison with the “split-phase” motors, because the use of capacitors in the auxiliary winding enables
(a) Provision of larger number of turns in the auxiliary winding
(b) A larger starting current to be drawn from the supply
(c) The torque-slip characteristic in general to get a shape to give a large starting torque
(d) The current division between the main and auxiliary windings to be conducive for the development of large starting torque

Ans:-D
8. If the load of a synchronous motor is increases while keeping the field excitation constant, then
(a) Power factor will increase and power angle will decrease
(b) Power factor will decrease and power angle will increase
(c) Both power factor and power angle will increase
(d) Both power factor and power angle will decrease

Ans:-C


9. A synchronous motor operates as a synchronous condenser when it is
(a) Operated at unity power factor
(b) under-excited
(c) Over-excited
(d) Connected in parallel with condensers

Ans:-C


10. An equipment has 0.8 per unit impedance on a base of 66KV, 100 MVA. It’s per unit impedances on a base of 33 KV, 100 MVA will be
(a) 0.4
(b) 0.8
(c) 1.6
(d) 3.2

Ans:-A


11. In a 3-phase power transformer, 5-limbed construction is adopted to
(a) Suppress the 5th and 7th harmonics
(b) Suppress the 3rd and its multiple harmonics
(c) Suppress all the orders of harmonics
(d) Increase the capacity of the transformer

Ans:-A

12. A transformer has a resistance of 2% and reactance of 4%. Its regulations at 0.8 power factor lagging a leading respectively are
(a) 4 per cent and — 0.8 per cent
(b) —4 per cent and 0.8 per cent
(c) — 0.8 per cent and 4 per cent
(d) 0.8 per cent and —4 per cent

Ans:-A

13. Consider the following statements:
The use of Delta-connected tertiary windings in star-star connected power transformers
1. Makes available supply for single-phase loads.
2. Suppresses harmonic voltages.
3. Allows flow of earth fault current for operation of protective devices
4. Provides low-reactance paths for zeros sequence currents.
Of the statements
(a) 1, 2 and 3 are correct
(b) 1, 3 and 4 are correct
(c) 2 and 4 are correct
(d) 1, 2, 3 and 4 are correct

Ans:-D


14. If dv / dt occurring across a thyristor exceeds its permissible value, then the thyristor will
(a) Remain in the forward blocking state without any damage
(b) Turn on only to get damaged
(c) Turn on but whether it gets damaged or not will depend on the final follow up current
(d) Not turn on but get damaged

Ans:-C



15. In a dc machine, the armature mmf is
(a) Rectangular and directed along the inter- polar axis
(b) Triangular and directed along the inter-polar axis
(c) Triangular and directed along the brush axis
(d) Rectangular and directed along the brush axis

Ans:-C


16. The average load current of a dc chopper feeding a pure resistive load is I amps. If a variable inductance connected in the load circuit Is progressively increased from zero value, keeping the duty ratio unchanged, then the average load current will
(a) Increase starting from 1
(b) Decrease with a starting value of 1
(c) Remain the same at 1
(d) Increase to some highest value of current and then decrease again to 1

Ans:-D

17. Consider the following statements:
The source inductance of an ac to dc line commutated phase controlled converter
1. limits dv / dt capability of thyristors.
2. Causes a voltage drop in the de terminal voltage.
3. Improves the line side power factor.
4. limits the range of firing angles.
5. reduces the line side power factor.
Of these statements
(a) 1, 3 and 4 are correct
(b) 1, 2 and 4 are correct
(c) 2 and 5 are correct
(d) 2, 4 and 5 are correct

Ans:-B




18. When starting a differentially connected compound motor, it Is desirable to short-circuit the series field winding to
(a) Avoid very high starting time
(b) Avoid excessive starting speed
(c) Prevent the motor from starting in the reverse direction
(d) Avoid heavy in-rush of current

Ans:-B

19. A single-phase voltage controller is employed for controlling the power flow from 206 V, 50 Hz source into a load consisting of R = 5 Ω and ω L = 12 Ω The value of maximum mis load current and the firing angle are respectively
(a) 260 / 10.9 A and 00
(b) 20 A and 0°
(c) 20 A and 90°
(d) 260 / 10.9 A and 90°

Ans:-C

20. The number of thyristors required for single- phase to single-phase cycloconverter of the midpoint and for three-phase to three-phase 3-pulse type of cycloconverter are respectively
(a) 4and6
(b) 4and4
(c) 4andl8
(d) None of the above

Ans:-C

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1. When bundle conductors are used in place of single conductors, the effective inductance and capacitance will respectively
(a) Increase and decrease
(b) Decrease and increase
(c) Decrease and remain unaffected
(d) remain unaffected and increase

Ans:-B


2. A balanced 3-phase, 3-wire supply feeds balanced star connected resistors. If one of the resistors is disconnected, then the percentage reduction in load will be
(a) 33(1/3)
(b) 50
(c) 66(2/3)
(d) 75

Ans:-A


3. A long overhead transmission line is terminated by its characteristic impedance. Under this operating condition, the ratio of the voltage to the current at dfferen1pñnts along the line will
(a) Progressively increase from the sending-end to the receiving-end
(b) Progressively increase from the receiving- end to the sending-end
(c) remain the same at the two ends, but be higher between the two ends being maximum at the centre of the line
(d) Remain the same at all points

Ans:-D


4. For a transmission line with negligible losses, the lagging reactive power (VAR) delivered at the receiving-end, for a given receiving-end voltage, is directly proportional to the
(a) Square of the line voltage drop
(b) Line voltage drop
(c) Line inductive reactance
(d) Line capacitive reactance

Ans:-B





5. Earth wire on EHV overhead transmission line is provided to protect the line against
(a) Lightning surges
(b) Switching surges
(c) Excessive fault voltages
(d) Corona effect

Ans:-A



6. Consider the following statements about distance relays
1. The effect of an arc may cause the relay to under reach.
2. The effect of an intermediate current source may cause the relay to overreach.
3. The effect of an intermediate load may cause the relay to under reach.
4. The presence of dc offset in the fault current may cause the relay to over- reach.
Of these statements:
(a) 2 and 3 are correct
(b) 1 and 4 are correct
(c) 1. 2 and 3 are correct
(d) 2, 3 and 4 are correct

Ans:-C





Directions: The following 13 items consist of two statements, one labelled the ‘Assertion A’ and the other labelled the ‘Reason R’. You are to examine these two statements carefully and decide f the Assertion A and the Reason R are individually true and if so, whether the Reason is a correct explanation of the Assertion. Select your answer to these Items using the codes given below and mark your answer sheet accordingly.
Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

7. Assertion (A): Whenever a synchro pair is used as an error detector, a two-phase ac motor may be used as an actuator.
Reason (R) : the synchro pair produces an error voltage which is suppressed carrier modulated and a two-phase ac motor could demodulate this.

Ans:-C


8. Assertion (A): The input impedance of a loss- less transmission line can have two limiting values, zero and infinity.
Reason (R) : These limiting values will depend upon whether the transmission line is open or shorted at the load end and whether the length of the line is an integral multiple of λ/4 where λ is the wavelength within the transmission line.

Ans:-A


9. Assertion (A) : In order to produce a light spot at the point at which the electron am strikes the CR0 screen, the inner surface of the screen is coated with a phosphor.
Reason (R) : The phosphor absorbs the kinetic energy of the bombarding electrons and reemits energy at a higher frequency

Ans:-B


10. Assertion (A) : Frequency modulation systems are more widely used than amplitude modulation systems.
Reason (R): Frequency modulation systems have less noise than amplitude modulation systems.

Ans:-C



11. Assertion (A): Low resistances are not measured by Wheatstone bridge arrangements.
Reason (R) : The effects of contact and lead resistances detrimental to low resistance measurements, are present in large amounts in Wheatstone bridge method.

Ans:-A


12. Assertion (A): Multistage dc amplifiers are invariably based on two-transistor differential amplifiers.
Reason (R): Two-transistor differential amplifiers have high gain and high CMRR.

Ans:-A


13. Assertion (A): DC shunt motors are usually fitted with interpoles.
Reason (R) : Interpoles increases the starting torque of dc shunt motors.

Ans:-C


14. Assertion (A): In a level compounded dc generator, the terminal voltage at full load is equal to the terminal voltage at no-load.
Reason (R): Under load conditions, the armature reaction increases the flux per pole and thus helps maintain a constant terminal voltage.

Ans:-A


15. Assertion (A): DC series motors are known to be capable of operating on ac supply as well. With a very minor modification, dc shunt motors can work on ac supply as well.
Reason (R): the direction of torque developed in a rotating machine remains unaltered if the directions of conductor current and air-gap flux are reversed simultaneously.

Ans:-C


16. Assertion (A): In the experimental determination of synchronous impedance of an ac generator, it is possible to take one set of data only from short- circuit test, and obtain there from the short circuit characteristic of the machine as a straight line passing through the origin of the plot.
Reason (R): During the short-circuit test, the magnetic circuit of an alternator; remains unsaturated even when the field excitation is high.

Ans:-B

17. Assertion (A): Under normal operating conditions, major portion of iron losses of an induction motor occurs in the stator.
Reason (R): The frequency of the rotor currents under normal operating conditions is very small.

Ans:-A

18. Assertion (A) Solid state regulators are finding favour in speed control of domestic fans, over conventional resistance and inductance type regulators.
Reason (R): Solid state regulators are compact, relatively less expensive, energy efficient, more reliable and afford noise-free operation.

Ans:-A

19. Assertion (A): The conductors are usually transposed in transmission lines.
Reason (R): The resistance of each phase has to be equal.

Ans:-C


20. For the network function
Z(s) = 2 (s2 + 1)(s2 + 9) / s(s2+4)
the value of the series capacitance in Foster Form I is
(a) 1/9 F
(b) 3/9 F
(c) 2/9 F
(d) 4/9 F

Ans:-C





21. Match List I with List II and select the correct answer using the codes given below the lists
List I
(Time functions)
A. e-2(t-2)
B. d (t2) / dt
C. t /2

List II
(Laplace transforms)
1. 2 / s2
2. 1 / s+2 e-2s
3. 1 / 2s2
4. 1 / 2s
Codes:
A B C
(a) 2 1 3
(b) 2 3 4
(c) 1 2 3
(d) 3 1 4

Ans:-A


22. When a constant voltage source V is connected to a series R-L circuit with zero initial stored energy in the inductor, the instantaneous value of power supplied to the inductor I is given by
(a) V2/R (e –Rl/L — e-2Rt/L)
(b) V2/R (1 — e-Rt/L)
(c) V2/R e-Rt/L
(d) V2/R(1 + e-Rt/L)

Ans:-B


23. Consider the following statements
In a series RLC resonant circuit, the bandwidth is
1. Directly proportional to resonant frequency
2. Inversely proportional to resonant frequency
3. Directly proportional to quality factor
4. Inversely proportional to quality factor
Of these statements:
(a) 2 and 3 are correct
(b) 2 and 4 are correct
(c) 1 and 3 are correct
(d) 1 and 4 are correct

Ans:-D





24. The instantaneous power taken by a balanced three-phase load supplied from a balanced three- phase source it
(a) Zero
(b) A constant
(c) A pulsating function with a non-zero average
(d) Alternating with a zero average

Ans:-B


25. The power in a 3-phase 3-wire load Is measured using two 100 W full-scale wattmeters W1 and W7 WI is of accuracy class ±1% and reads 100 W. W2 is of accuracy class ±0.5% and reads —50 W. Then the uncertainty In the computation of total power it
(a) ± 1.5%
(b) ± 0.5%
(c) ±4%
(d) ±3%

Ans:-D

Solved electrical engineering for IES

 Solved electrical engineering for IES
SAMPLE PAPER
1. A current carrying coil is subjected to a uniform magnetic field. The coil will orient so that its
plane becomes    ?
(a) inclined at 45° to the magnetic field
(b) inclined at any arbitrary angle to the
magnetic field
(c)   parallel to the magnetic field
(d)   perpendicular to magnetic field
Ans:c
2. Tesla is the unit of
(a)    magnetic flux
(b)    magnetic field
(c)    magnetic induction
(d)    magnetic moment
Ans:b
3. Energy in a current carrying coil is stored in the
form of   ?
(a) electric field
(b) magnetic field
(c) dielectric strength
(d) heat
Ans:b
4. The total charge induced in a conducting loop when it is moved in magnetic field depends on?
(a) the rate of change of magnetic flux
(b) initial magnetic flux only
(c) the total change in magnetic flux
(d) final magnetic flux only.
Ans:c
5. The magnetic induction at a point P which is at the distance of 4 cm from a long current carrying wire is 10^-3 T. The field of induction at a distance 12 cm from the current will be ?
(a) 3.33 x 10^-4 T
(b) 1.11x 10^-4 T
(c) 3×10^-3 T
(d) 9×10^-3 T
Ans:a
6. A charge moving with velocity v in X-direction is subjected to a field of magnetic induction in negative X-direction. As a result, the charge will
(a) remain unaffected
(b) start moving in a circular path in Y—Z plane
(c) retard along X-axis
(d) moving along a helical path around X-axis
Ans:a
7. A uniform magnetic field acts right angles to the direction of motion of electrons. As a result, the electron moves in a circular path of radius 2cm. If the speed of electrons is doubled, then the radius of the circular path will be ?
(a)2.0 cm
(b) 0.5 cm
(c)4.0cm
(d) 1.0cm
Ans:c
8. A deuteron of kinetic energy 50 keV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to magnetic field B. The kinetic energy of the proton that describes a circular orbit of radius 0.5 metre in the same plane with
the same B is
(a)25 keV
(b) 50 keV
(c)200 keV
(d) 100 keV
Ans:d
9. A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in uniform magnetic field of induction 2 Tesla. The magnetic field is perpendicular to the length of the wire. The force on the wire is ?
(a) 2.4N
(b) 1.2N
(c) 3.0 N
(d) 2.0 N
Ans:b
10. To convert a galvanometer into an ammeter, one needs to connect a ?
(a) low resistance in parallel
(b) high resistance in parallel
(c) low resistance in series
(d) high resistance in series.
Ans:a
11. A coil carrying electric current is placed in uniform magnetic field
(a) torque is formed
(B) e.m.f is induced
(c) both (a) and (b) are correct
(d) none of the above
Ans:a
12. The magnetic field at a distance ‘r’ from a long wire carrying current ‘i’ is 0.4 Tesla. The magnetic field at a distance ‘2r’ is ?
(a)0.2Tesla
(b) 0.8 Tesla
(c)0.1 Tesla
(d) 1.6 Tesla
Ans:a
13. A electron enters a region where magnetic (B) and electric (E) fields are mutually
perpendicular, then ?
(a) it will always move in the direction of B
(b) it will always move in the direction of E
(c) it always possesses circular motion
(d) it can go un deflected also.
Ans:d
14. A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of I mm diameter carrying same current. The strength of magnetic field far away is?
(a) twice the earlier value
(b) same as the earlier value
(c) one-half of the earlier value
(d) one-quarter of the earlier value
Ans:b
15. At what distance from a long straight wire carrying a current of 12 A will the magnetic field
be equal to 3×10^-6 Wb/metre Square
(a) 8×10^-2 m
(b) 12×10^-2 m
(c)18x 10^-2 m
(d) 24×10^-2 m
Ans:a
16. An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to ?
(a) √(B/v)
(b) B/v
(c) √(v/B)
(d)v/B
Ans:d
17. A 10 eV electron is circulating in a plane at right angles to a uniform field at magnetic induction 10^-4 Wb/m² (= 1.0 gauss). The orbital radius of the electron is ?
(a) 12cm
(b) 16cm
(c) 11cm
(d) 18cm
Ans:c
18. A galvanometer acting as a voltmeter will have?
(a) a low resistance in series with its coil.
(b) a high resistance in parallel with its coil
(c) a high resistance in series with its coil
(d) a low resistance in parallel with its coil
Ans:c
19. A beam of electrons is moving with constant velocity in a region having simultaneous perpendicular electric and magnetic fields of strength 20 Vm^-1 and 0.5 T respectively at right angles to the direction of motion of the electrons. Then the velocity of electrons must be?
(a) 8m/s
(b) 20 m/s
(c) 40m/s
(d) 1/40 m/s
Ans:c
20. A galvanometer of resistance 20 Ohms gives full scale deflection with a current of 0.004 A. To convert it into an ammeter of range 1 A, the required shunt resistance should be?
(a) 0.38 Ohms
(b) 0.21 Ohms
(c) 0.08 Ohms
(d) 0.05 Ohms
Ans:c
21. A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is ?
(a) 4B
(b) B/2
(c) B
(d) 2B
Ans:c
22. A positively charged particle moving due east enters a region of uniform magnetic field directed vertically upwards. The particle will
(a) continue to move due east
(b) move in a circular orbit with its speed unchanged
(c) move in a circular orbit with its speed increased
(d) gets deflected vertically upwards.
Ans:b
23. Two long parallel wires are at a distance of 1 metre. Both of them carry one ampere of current The force of attraction per unit length between the two wires is?
(a)2 x10^-7 N/m
(b) 2 x10^-8 N/m
(c) 5×10^-8 N/m
(d)10^-7 N/m
Ans:a
24. A galvanometer having a resistance of 8 ohms is shunted by a wire of resistance 2 ohms. If the total current is 1 amp, the part of it passing through the shunt will be?
(a)0.25 amp
(b) 0.8 amp
(c)0.2 amp
(d) 0.5 amp
Ans:b
25. A coil of one turn is made of a wire of certain length and then from the same length a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centres will be?
(a)2:1
(b)1:4
(c)4:1
(d)1:2
Ans:b
26. Magnetic field intensity in the centre of coil of 50 turns, radius 0.5 m and carrying a current of
2A is ?
(a) 0.5 x 10^-5 T
(b) 1.25x 10^-4 T
(c) 3x 10^-5 T
(c) 4 x 10^-5 T
Ans:b
27. When a proton is accelerated through I V, then its kinetic energy will be?
(a)1840 eV
(b) 13.6eV
(c)1 eV
(d) 0.54eV
Ans:c
28. If a long hollow copper pipe carries a current,thin magnetic field is produced
(a)inside the pipe only
(b)outside the pipe only
(c)both inside and outside the pipe
(d) no where
Ans:b
29. A charged particle moves through a magnetic field in a direction perpendicular to it. Then the
(a) velocity remains unchanged
(b) speed of the particle remains unchanged
(c) direction of the particle remains unchanged
(d) acceleration remains unchanged
Ans:b
30. Two long parallel wires P and Q are both perpendicular to the plane of the paper with distance of 5 m between them. If P and Q carry current of 2.5 amp and 5 amp respectively in the same direction, then the magnetic field at a point half-way between the wires is ?
(a)3µ/2∏
(b)µ/∏
(c)√3µ/2∏
(d)µ/2∏
Ans:a
31. A proton moving with a velocity 3 x 10⁵ m/s enters a magnetic field of 0.3 Tesla at an angle of 30° with the field. The radius of curvature of its path will be (e/m for proton – 10⁸ C/kg)
(a)2cm
(b) 0.5 cm
(c)0.02 cm
(d) 1.25 cm
Ans:b
32. A charged particle of charge q and mass m enters perpendicularly in a magnetic field B. Kinetic energy of the particle is E; then frequency of rotation is?
(a)qB/m∏
(b) qB/2m∏
(c)qBE/2m∏
(d) qB/2E∏
Ans:b
33. A galvanometer can be converted into a voltmeter by connecting?
(a) A high resistance in parallel
(b) A low resistance in series
(c) A high resistance in series
(d) A low resistance in parallel
Ans:c
34. A wire carries a current. Maintaining the same current it is bent first to form a circular plane coil of one turn which produces a magnetic field B at the centre of the coil. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre of the double loop, caused by the same current is ?
(a)4B
(b) B /4
(c) B/2
(d) 2B
Ans:a
35.A bar magnet is oscillating in earth’s magnetic field with a period T. What happens to its period of motion, if its mass is quadruped ?
(a) Motion remains simple harmonic with new period =T/2
(b) Motion remains simple harmonic with new period = 2 T
(c) Motion remains simple harmonic with new period =4T
(d) Motion remains simple harmonic and the period stays nearly constant
Ans:b
36. The work done in turning a magnet of magnetic moment M by an angle of 90° from the meridian, is n times the corresponding work done to turn it through an angle of 60°.
The value of n is given by
(a)2
(b) 1
(c) 0.5
(d) 0.25
Ans:a
37 . For protecting a sensitive equipment from the external electric arc, it should be ?
(a) Wrapped with insulation around it when passing current through it
(b) Placed inside an iron can
(c) Surrounded with fine copper sheet
(d) Placed inside an aluminium can
Ans:b
38. If a diamagnetic substance is brought near north or south pole of a bar magnet, it is?
(a) attracted by the poles
(b) repelled by the poles
(c) repelled by north pole and attracted by the south pole
(d) attracted by the north pole and repelled by the south pole
Ans:b
39. Current i is flowing in a coil of area A and number of turns N, then magnetic moment of
the coil is M= ?
(a) NiA
(b) Ni/A
(c)Ni/√A
(d) N²Ai
Ans:a
40. Two magnets of magnetic moments M and 2M are placed in a vibration magnetometer, with the identical poles in the same direction. The time period of vibration is T₁. If the magnets are placed with opposite poles together and vibrate with time period T₂ then ?
(a) T₂ is infinite
(b) T₂=T₁
(c)T₂>T₁
(d) T₂ is less than T₁
Ans:c
41. A diamagnetic material in a magnetic field moves
(a) perpendicular to the field
(b) from stronger to the weaker pans of the field
(c) from weaker to the stronger parts of the field
(d) in none of the above directions
Ans:b
42. According to Curie’s law, the magnetic susceptibility of a substance at an absolute
temperature T is proportional to?
(a) T²
(b) 1/T
(c) T
(d) 1/T²
Ans:b

Elecrtical Engineering Questions For UPSC IES

Elecrtical Engineering Questions For UPSC IES

Engineers Fully Solved
Electrical Engineering: Objective Questions with Answers
OBJECTIVE QUESTIONS ADVANCED ELECTRICAL ENGINEERING
Electrical Engineering Interview Questions.
These MCQ questions are very useful for
UPSC IES Exam
UPSC Civil Services Prelims Electrical Engg
1.If the applied voltage of a certain transformer is increased hr 50% and the frequency is reduced to 50% (assuming that the magnetic circuit remains unsaturated), the maximum core flax density will
(a) change to three times the original value
(b) change to 1.5 times the original value
(c) change to 0.5 times as the original value
(d) remain the same as the original value
2. The low—voltage winding of a core type transformer is subdivided into two equal halves, each of half the original width of the single winding will the high voltage winding in between (instead of having the usual construction of low-voltage winding adjacent to the core and surrounded by the high-voltage winding). Such an interlacing of coils would make the combined primary and secondary leakage reactance (in terms of primary) nearly.
(a)twice
(b) equal
(c)half
(d) one -fourth
3. Two 3-limb, 3-phase delta-star connected transformers are supplied from the same source. One of the transformers is of. Dy I and the other is of Dy II / connection. The phase difference between the corresponding phase voltages of the secondaries would he
(a) 0°
(b) 30°
(c) 60°
(d) 120°
4. In a transformer fed from a fundamental frequency voltage source, the source of harmonics k the
(a) overload
(b) poor insulation
(c) iron loss
(d) saturation of core
5. A 40 kVA transformer/ a core loss of400 W and a full load copper of of 800 W. The proportion of full-load at maximum efficiency is
(a)50%
(b) 62.3%
(c) 70.7%
(d)100 %
6.A single phase transformer has rating of 15 KVA 600 / 120 V. It is recommended as an auto transformer to supply at 720 V from a 600 V primary source. The maximum load it can supply is ?
(a)90 kVA
(b)18 kVA
(c)15 kVA
(d) 12 kVA
7. Equalizing pulses in TV are placed during the
(a) vertical blanking period
(b) horizontal blanking period
(c)serration
(d) horizontal retrace
8. The most useful approach to radar system for monitoring the speed of moving vehicles is:
(a) Pulsed radar
(b) Monopulse
(c)Doppler radar
(d) Auto tracking radar
9. A. dc shunt generator, when driven at its rated speed, is found to he not generating any voltage. Which of the following would account for this?
I. There is no residual magnetism
2. The connection of the field winding is not proper with respect to the armature terminals.
3. The resistance of the field circuit is greater than the critical field resistance.
4. The load resistance is less than the critical armature resistance.
Select the correct answer using the codes given below:
Codes:
(a)3 and 4
(b)l,2 and 4
(c)1,2 and 3
(d)l.2,3 and 4
10. To have spark/as commutation, the armature reaction effect in a dc machine is neutralised by
(a) using compensating winding and commutating poles
(b) Shifting the brush axis from the geometrical neutral axis to the magnetic neutral axis
(c) fixing the brush axis in line with the pole axis
(d) increasing the field excitation
11.In a dc shunt general or working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will
(a)improve but terminal voltage will fall -
(b)worsen and terminal voltage will fall
(c) improve and terminal voltage will rise
(d) worsen and terminal voltage will rise
12. Consider the following statements:
The maximum range of radar can be increased by
1. increasing the peak transmitted power
2. increasing the gain of the receiver
3. increasing the diameter of the antenna
4. reducing the wavelength used
Of these statements
(a) 1, 3 and 4 are correct
(b) 1, 2, 3 and 4 are correct
(c) 2 and 4 are correct
(d)1 and 3 are correct
13. Consider the following statements about broadband communication using submarine cables:
1. A submarine cable repeater contains filters for the two directions of transmits
2. Armored submarine cable is used for the shallow-shore ends of the cable.
3. Fibre optic submarine cable is used to prevent inadvertent ploughing in of the cable
Of these statements
(a) 1 and 2 are correct
(b) 2 and 3 are correct
(c) 1 and 3 are correct
(d) 1, 2 and 3 are correct
14. A dc overcompounded generator was operating satisfactorily and supplying power to an infinite bus when the prime mover failed to supply any mechanical power. The machine would then run as a ?
(a) cumulatively compounded motor with speed reversed
(b) cumulatively compounded motor with direction of rotation as before
(c) differentially compounded motor with speed reversed
(d) differentially compounded motor with direction of speed as before.
15 To couple a coaxial line to a parallel wire line, It is best to use a
(a) slotted line
(b) balun
(c)directional coupler
(a) quarter-wave transformer
16. When a synchronous motor is running at synchronous speed, the damper winding produces
(a) damping toruqe
(b) eddy current torque
(c)torques aiding the developing torque
(d) no torque
17. For a given developed power, a synchronous motor operating from a constant voltage and constant frequency supply, will draw the minimum and maximum armature currents, Imin and Imax respectively, corresponding to?
(a)Imin at unity pf, but Imax at zero pf
(b) Imax at unity p, but Imin at zero p1
(c) both Imin and Imax at unity pf
(d )both Imin and Imax at zero pf
18. Consider the folio wing statements regarding an RC phase-shift oscillator:
1. The amplifier gain is positive
2. The amplifier gain is negative.
3. The phase shift introduced by the feedback network is 180
4. The phase shift introduced by the feedback network is 360
Of these statements
(a) 1 and 3 are correct
(b) 2 and 3 are correct
(c) 2 and 4 are correct
(d) 1 and 4 are correct
19 While conducting a “slip “ test for determination of direct and quadrature axis synchronous reactance ‘Xd’ and ‘Xq’ of salient pole synchronous machine, the rotor of the machine is run with a slip ‘s’ and stator supply frequency ‘f’. The frequency of
1. voltage induced across open field terminals,
2. envelope of the armature terminal voltage.
3. envelope of the armature current, and
4. armature current
will be respectively
(a) sf, sf,sf and f
(b) sf, f,sf and f
(c) f, sf,f and af
(d) f, (1-s)f,(2-s)f and sf
20. If two induction motors A and B are identical except that the air-gap of motor ‘A ‘ is 59% greater than that of motor ‘B’, then
(a) the no-load power factor of A will be better than that of B.
(b) the no-load power factor of A will be poorer than that of B.
(c) the core losses of A will be more than those of B
(d) the operating flux of A will be smaller than that of B.
21 A 6-pole, 50 Hz, 3-phase synchronous motor and an 8-pole, 50 Hz. 3—phase slipring induction motor are mechanically coupled and operate on the some 3-phase, 50 Hz supply system If they are left open-circuited, then the frequency of the voltage produced across any two slip rings would be?
(a) 12.5 Hz
(b) 25.0 Hz
(c) 37.5 Hz
(d) 50.0 Hz
22. Which of the following statements regarding skewing of motor bars in a squirrel-cage induction motor are correct?
I. It prevents cogging;
2. It produces more uniform torque.
3. it increases starting torque.
4. It reduces motor ‘hum’ during its operation.
Select the correct answer using the codes given below.
Codes:
(a)2,3 and 4
(b) l,2 and 3
(c)1,3 and 4
(d) l,2 and 4
23. The rotor power output of a 3-phase induction motor is 15kW and the corresponding slip is 4%. The rotor copper loss will be
(a) 600 W
(b) 625 W
(c) 650 W
(d) 700 W
24. If an input signal with non-zero dc component is applied to a low pass RC network, the dc component in the output will be ?
(a) the same as that in the input
(b) less than that in the input
(c) more than that in the input
(d) zero
25. A 3 phase wound rotor induction motor, when started with load connected to its shaft, was found to start but settle down at about half synchronous speed. If the rotor winding as well as the stator winding were star connected, then the cause of the malfunction could be attributed to
(a) one of the stator phase windings being short–circuited
(b) one of the supply fuses being blown
(c) one of the rotor phases being open-circuited
(d) two of the rotor phases being open circuited
26. Consider the following statements regarding fractional horse power shaded-pole motor:
1. Its direction of rotation is from unshaded to shaded portion of the poles.
2.. Its direction of rotation is from shaded to unshaded portion of the poles.
3. It can remain stalled for short periods without any harm.
4. It has a very poor power factor.
Of these statements
(a) 1, 3 and 4 are correct
(b) 2, 3 and 4 are correct
(c) 2 and 4 are correct
(d) 1 and 3 are correct
27. In the case of a converter-inverter speed control arrangement f an induction motor operating with v/f constant and with negligible stator impedance.
(a) the maximum torque is independent of frequency
(b) the maximum torque is proportional to frequency
(c) the slip at maximum torque is proportional to frequency
(d) the starting torque is proportional to frequency
28 An amplifier with mid-band gain A = 500 has negative feedback beta = 1/100 the upper cut-off without feedback were at 60 kHz, then with feedback it would become
(a) 10kHz
(b) 12kHz
(c) 300 kHz
(d) 360 kHz
29. If the discharge is 1 m cube and the head of water is 1 m then the power generated by the alternator in one hour (assume 100% efficiency of generator and turbine) will be
(a) 10kW
(b) 73/75kW
(c) 746/75kW
(d) 100kw
30. Control rods used In unclear reactors are made of
(a) zirconium
(b) boron
(c) beryllium
(d) lead
31. if alpha = 0.98, Ico=6 microA I beta =100 microA for a transistor, Then the value of Ic will he
(a) 2.3mA
(b) 3.lmA
(c) 4.6mA
(d) 5.2mA
32. In a 3-core extra-high voltage cable, a metallic screen around each core-insulation is provided to
(a) facilitate heat dissipation
(h) give mechanic strength
(c) obtain radial electric stress
(d) obtain longitudinal electric stress
33. Galloping In transmission line conductors arises generally due to
(a) asymmetrical layers of ice formation
(b) vortex phenomenon in light winds
(c) heavy weight of the line conductors
(d) adoption of horizontal conductor configurations
34.. In a 3- phase rectifier circuit, thyristor number 1, 2 and 3 are connected respectively to R, Y and B phases of the star-connected transformer secondary. When the current is being commutated front thyristor No. 1 to No. 2, the effect of the transformer leakage and the ac system Inductance will be such that it will?
(a) Prolong the conduction in No. 1 and delay the turn on of No. 2 correspondingly.
(b) stop the conduction in No. 1 at the scheduled time, but delay the turn on of No. 2
(c) produce conduction in both No. 1 and No. 2 in parallel for an overlapping period through a transient
(d) double the voltage output through a commutation transient
35. The incremental generating costs of two generating units are given by
IC1=0.10 X + 20 Rs /MWhr
IC1=0.15 Y + 18 Rs /MWhr
where X and V are power generated by the two units in MW.
For a total demand of 300 MW, the value (in MW) of X and Y will be respectively
(a) 172 and 123
(b) 123 and 172
(c) 175 and 125
(d) 200 and 100
36. Consider the following statements:
To provide reliable protection for a distribution transformer against over voltages using lightning arrestors, it is essential that the
1. lead resistance is high.
2. distance between the transformer and the arrestor is small
3. transformer and the arrestor have a common inter-connecting ground.
4. Spark over voltage of the arrestor is greater than the residual voltage.
Of these statements
(a) 1, 3 and 4 are correct
(b) 2 and 3 are correct
(c)2, 3 and 4 are correct
(d) 1 and 4 are correct
37. The reflection coefficient of a short-circuited line is
(a) -1
(b) 1
(c) 0.5
(d) zero
38.Iif an intrinsic semiconductors is doped with a very small amount of born then in the extrinsic semiconductor so farmed, the number of electrons and holes will
(a)decrease
(b) increase and decrease respectively
(c)increase
(d) decrease and increase respectively
39. Hollow conductors are used in transmission lines to
(a) reduce weight of copper
(b) improve stability
(c) reduce corona
(d) increase power transmission capacity
40. In the solution of load-flow equation, Newton-Raphson (NR) method is superior to the Gauss- Seidel (GS) method, because the
(a) time taken to perform one iteration in the NR method is less When compared to the time taken in the OS method
(b) number of iterations required in the NR method is more when compared to that in the GS method
(c) number of iterations required is not independent of the size of the system in the NR method
(d) convergence characteristics of the NR method are not affected by the selection of slack bus
41. In a synchronous generator, a divided winding rotor is preferable to a conventional winding rotor because of
(a) higher efficiency
(b) increased steady-state stability limit
(c) higher short-circuit ratio
(d) better damping
42. Consider the following statements regarding speed control of induction motors by means of external rotor resistors:
1. Reduction in speed is accompanied by reduced efficiency.
2. With a large resistance in the rotor circuit, the speed would vary considerably with variation in torque
3. The method is very complicated
The Disadvantages of such a method of speed control would include
(a) l and 2
(b) 2 and 3
(c) l and 3
(d) 1,2 and 3
43. Zero sequence currents can flow from a line into a transformer bank if the windings are in ?
(a) grounded star/delta
(b) delta/star
(c) star/grounded star
(d) delta/delta
44. When a line to ground fault occurs, the current in a faulted phase is 100 A. The Zero Sequence current in this case will be
(a) zero
(b) 33.3 A
(c) 66.6A
(d) 100 A
45. Consider the following statements:
Switched mode power supplies are preferred over the continuous types, because they are
1. suitable for use in both ac and dc.
2; more efficient,
3. suitable for low-power circuits.
4. suitable for high-power circuits.
Of these statements
(a) 1 and 2 are correct
(b) 1 and 3 are correct
(c) 2 and 3 are correct
(d) 2 and 4 are correct
46. The power generated by two plants are P1 = 50MW, P2= 40 MW.
If the loss coefficients are B11 = 0.001, B22 = 0.0025 and B12 = -0.0005, the power loss will be
(a)5.5 MW
(b) 6.5 MW
(c) 4.5Mw
(d) 8.5 MW
47. In dc choppers, per unit ripple is maximum when then duty cycle is?
(a) 0.2
(b) 0.5
(c) 0.7
(d) 0.9
48. The following data pertain to two alternators working in parallel and supplying a total load of 80 MW:
Machine 1 : 40 MVA with 5% speed regulation
Machine 2: 60 MVA with 5% speed regulation
The load sharing between machines 1 and 2 will be
(a)P1/48MW, P2/32MW
(b) 40MW. 40MW
(c)30MW,50MW
(d) 32 MW. 48MW
49. The per unit impedance of a synchronous machine is 0.242. If the base voltage is Increased by 1.1 times, the per unit value will be
(a)0.266
(b) 0.242
(c)0.220
(d) 0.200
50. A 3-pulse converter feeds a pure resistive load at a firing angle of alpha = 60°. The average value of current flowing in the load is 10 A, If a very large inductance is connected in the load circuit, then the
(a) average value of current will remain as 10 A
(b) average value of current wilt become greater than 10 A
(c) average value of current will become less than 10 A
(d) trend of variation of current cannot be predicted unless the exact value of the inductance connected is known

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