Electrical Basic Questions 14

Electrical Basic Questions 14

1)   “ Total electric flux through any closed surface is equal to the charge enclosed by that surface ”. This is

a. Lenz’s law
b. Gauss’s law
c. Maxwell’s law
d. Faraday’s law

ANSWER: Gauss’s law

2)   Gauss’s law is applicable for

a. Only point charge
b. Infinite line charge
c. Infinite sheet of charge
d. All of these

ANSWER: All of these

3)   The potential difference between two points is given by

a. V = E / Q
b. V = W / Q
c. V = Q / E
d. V = Q / W

ANSWER: V = W / Q

4)   For forming an electric dipole between two point charges separated by a small distance, the two point charges are of

a. Unequal magnitude and opposite sign
b. Unequal magnitude but same sign
c. Equal magnitude and same sign
d. Equal magnitude but opposite sign

ANSWER: Equal magnitude but opposite sign

5)   The amount of work done in moving a charge from one point to another along an equipotential line or surface charge is

a. Zero
b. Infinity
c. One
d. Two

ANSWER: Zero

Electrical Basic Questions 14

6)   In ac circuit the maximum current required is

a. Equal to the effective current
b. 1.414 times the effective current
c. Twice the effective current
d. 1.732 times the effective current

ANSWER: 1.414 times the effective current

7)   A vector quantity has

a. Only magnitude
b. Only direction
c. Both (a) and (b)
d. None of these

ANSWER: Both (a) and (b)

8)   The phasor current through a 200 ohm resistor assuming a voltage of 200Arms at an angle of zero degree applied across it is

a. 1Arms at an angle of zero degree
b. 1Arms at an angle of 45 degree
c. 1Arms at an angle of 90 degree
d. 1Arms at an angle of 180 degree

ANSWER: 1Arms at an angle of zero degree

9)   If the number of turns, area and current of an ac circuit is doubled then the new inductance will be

a. Equal to the former
b. Twice of the former
c. Four times the former
d. Half of the former

ANSWER: Four times the former

10)   When an ac power is applied to a reactive load, then the voltage is

a. In phase with the current
b. 90 degree out of phase with the current
c. 180 degree out of phase with the current
d. 270 degree out of phase with the current

ANSWER: 90 degree out of phase with the current

Electrical Basic Questions 14

11)   If the number of conductors and speed of a lap wound generator is doubled then the generated emf will be

a. Remains same
b. Twice of the former
c. Four times of former emf
d. Half of the former emf

ANSWER: Four times of former emf

12)   When the motor runs on no load, then

a. Back emf is almost equal to applied voltage
b. Back emf will be greater than applied voltage
c. Back emf will be less than applied voltage
d. None of these

ANSWER: Back emf is almost equal to applied voltage

13)   The field winding of dc series motor consists of few turns of

a. Thin wire with low resistance
b. Thick wire with low resistance
c. Thin wire with high resistance
d. Thick wire with high resistance

ANSWER: Thick wire with low resistance

14)   If the armature current of dc series motor has become twice then the torque will become

a. Twice of the former
b. Four times of the former
c. One fourth of the former
d. Remains same

ANSWER: Four times of the former

15)   For application in electric locomotives or for traction purposes, the most suitable motor is

a. Dc series motor
b. Differentially compounded motor
c. Cumulatively compounded motor
d. None of these

ANSWER: Dc series motor

Electrical Basic Questions 14

16)   In order to bring the pointer to rest within a short time,

a. Gravity control is required
b. Damping control is required
c. Spring control is required
d. All of these

ANSWER: Damping control is required

17)   Among the following damping method, the most effective and efficient damping is

a. Air friction damping
b. Fluid friction damping
c. Eddy current damping
d. None of these

ANSWER: Eddy current damping

18)   In dynamometer type wattmeter, at equilibrium

a. Tc > Td
b. Tc < Td
c. Tc = Td
d. None of these

ANSWER: Tc = Td

19)   The moving system of induction type single – phase energy meter consists of

a. One pointer and two control spring
b. One pointer and one control spring
c. Two pointer and two control spring
d. No pointer and no control spring

ANSWER: No pointer and no control spring

20)   The braking torque of induction type single – phase energy meter is

a. Directly proportional to the flux
b. Inversely proportional to the flux
c. Directly proportional to the square of the flux
d. Inversely proportional to the square of the flux

ANSWER: Directly proportional to the square of the flux

Electrical Basic Questions 14

21)   The power curve for a purely resistive circuit is zero only when

a. Current is zero
b. Voltage is zero
c. Both current and voltage is zero
d. None of these

ANSWER: Both current and voltage is zero!

22)   The power absorbed by a pure inductive circuit and pure capacitive circuit is

a. Zero and non zero
b. Non zero and zero
c. Non zero and non zero
d. Zero and zero

ANSWER: Zero and zero

23)   The product of rms values of current and voltage is called as

a. Real power
b. Apparent power
c. Reactive power
d. Polar curves

ANSWER: Apparent power

24)   The net power in a series R-C circuit is

a. Zero
b. Positive
c. Negative
d. None of these

ANSWER: Positive

25)   For solving parallel ac circuit, the method used is

a. Vector method
b. Admittance method
c. Symbolic or j – method
d. All of these

ANSWER: All of these

Electrical Basic Questions 14

26)   For improving the soil condition and efficiency of earthing system, the pit area around the G.I. pipe is filled with

a. Mixture of copper and nickel
b. Mixture of chloride and sodium
c. Mixture of aluminium and sulphate
d. Mixture of salt and coal

ANSWER: Mixture of salt and coal

27)   The fusing current of a fuse depends on its

a. Material and its length
b. Length and its diameter
c. Material and diameter
d. Material, length and diameter

ANSWER: Material, length and diameter

28)   The wrong statement among the following is

a. A fuse can be fitted in an outlet socket
b. A fuse should not get overheated
c. The current rating of fuse should not exceed the rating of the smallest cable protected
d. Fuse having rating less than 3 A can be used in radio

ANSWER: A fuse can be fitted in an outlet socket

29)   In HRC fuses, the space within the body surrounding the element is usually filled with

a. Silver
b. Zinc
c. Quartz
d. Copper

ANSWER: Quartz

Electrical Basic Questions 14

30)   For extinguishing arc in an high voltage fuses, the element can be immersed in

a. Oil
b. Carbon tetrachloride
c. Carbon tetrafloride
d. Only (a) and (b)

ANSWER: Only (a) and (b)

31)   The expression for total power output of a delta connected system in terms of phase voltage and current is given by

a. 3VpIpcos∅
b. √3VpIpcos∅
c. 1/√ 3VpIpcos∅
d. 1/3 x VpIpcos∅

ANSWER: 3VpIpcos∅

32)   In delta connected system, the potential difference between line outers is

a. Equal to the phase voltage
b. Greater than the phase voltage
c. Less than the phase voltage
d. None of these

ANSWER: Equal to the phase voltage

33)   By using two wattmeter method, power can be measured in

a. 3 – phase, 2 – wire system
b. 3 – phase, 3 – wire system
c. 3 – phase, 4 – wire system
d. All of these

ANSWER: 3 – phase, 3 – wire system

34)   The two wattmeter method is applicable for

a. Only star connected system
b. Only delta connected system
c. Both star connected and delta connected system
d. None of these

ANSWER: Both star connected and delta connected system

35)   In a balanced 3-phase system, if one of the two wattmeter’s reading is negative then the

a. Reading should be taken as it is
b. Reading should be taken after reversing the pressure coil
c. Reading should be taken after reversing the current coil
d. All of these

ANSWER: Reading should be taken after reversing the pressure coil

Electrical Basic Questions 14

36)   From full load to no load, the change of terminal voltage is more in case of

a. Lagging power factor
b. Leading power factor
c. Unity power factor
d. Both lagging and leading power factor compared to unity power factor

ANSWER: Both lagging and leading power factor compared to unity power factor

37)   The synchronous generator is also called an

a. AC generator
b. Alternator
c. DC generator
d. Only (a) and (b)

ANSWER: Only (a) and (b)

38)   In India, the synchronous generator generates

a. 11 kilo – volts
b. 33 kV
c. 66 kV
d. Either (a) or (b)

ANSWER: Either (a) or (b)

39)   The non salient pole type synchronous generator is driven by

a. Hydraulic turbines
b. Diesel engines
c. Steam engines
d. All of these

ANSWER: Steam engines

40)   The number of cycles of the induced emf per second is equal to

a. No. of cycles per revolutions x no. of revolutions per second
b. No. of cycles per second x no. of revolutions per second
c. No. of cycles per revolutions x no. of revolutions per hour
d. No. of cycles per revolutions / no. of revolutions per second

ANSWER: No. of cycles per revolutions x no. of revolutions per second

41)   Copper losses occurs due to ohmic resistance in

a. Primary winding
b. Secondary winding
c. Both primary and secondary winding
d. None of these

ANSWER: Both primary and secondary winding

Electrical Basic Questions 14

42)   Efficiency of a transformer is maximum at

a. Leading power factor
b. Lagging power factor
c. Unity power factor
d. None of these

ANSWER: Unity power factor

43)   If the transformer is loaded then the secondary terminal voltage falls for and rises for

a. Lagging power factor, leading power factor
b. Lagging power factor, unity power factor
c. Unity power factor, lagging power factor
d. Leading power factor, lagging power factor

ANSWER: Lagging power factor, leading power factor

44)   Copper losses is proportional to

a. kVA
b. square of kVA
c. cube of kVA
d. none of these

ANSWER: square of kVA

45)   The efficiency of the transformer will be maximum when

a. Iron losses is equal to the twice of the copper losses
b. Copper losses is equal to the twice of the iron losses
c. Iron losses is equal to the copper losses
d. All of these

ANSWER: Iron losses is equal to the copper losses

46)   The frequency of the induced emf in an induction motor is

a. Greater than the supply frequency
b. Lesser than the supply frequency
c. Same as the supply frequency
d. None of these

ANSWER: Same as the supply frequency

Electrical Basic Questions 14

47)   In an induction motor, rotor speed is always

a. Less than the stator speed
b. More than the stator speed
c. Equal to the stator speed
d. None of these

ANSWER: Less than the stator speed

48)   Slip of an induction motor increases with

a. increase in current and decrease in torque
b. increase in current and torque
c. decrease in current and torque
d. decrease in current and increase in torque

ANSWER: increase in current and torque

49)   The frequency of rotor current in an induction motor is

a. slip times the frequency of stator current
b. slip times the frequency of supply
c. One by slip times the frequency of stator current
d. One by slip times the frequency of supply

ANSWER: slip times the frequency of supply

50)   Slip ring induction motor has

a. Low starting torque
b. Medium starting torque
c. High starting torque
d. None of these

ANSWER: High starting torque

Electrical Basic Questions 14