Electrical measurements MCQ Quiz Hub

1. The secondary circuit of a C.T. is open when?
a very high flux density is produced
a very low flux density is produced
a moderate flux density is produced
no flux density is produced

2. High flux density leads to _____
a decreased voltage in the secondary
a decreased voltage in the primary
a increased voltage in the secondary
a decreased voltage in the primary

3. When primary current flows, secondary circuit should be open.
True
False
all of the above
None of the mentioned

4. High magnetizing forces in the core when removed suddenly lead to _____
no residue
partial residual magnetism
rupture of the device
residual magnetism

5. The secondary winding of a C.T. ________
can be shorted
can’t be shorted
can be opened
can’t be opened

6. The secondary winding of a C.T. is opened when?
C.T. is magnetised
C.T. is demagnetised
C.T. is shorted
C.T. is opened

7. The rectangular type of C.T. is built of ______
L shaped windings
T shaped windings
A shaped windings
Z shaped windings

8. Potential transformers are used to measure ______
high voltages
low voltages
high currents
low currents

9. Potential transformers are used with ______
high range voltmeter
low range voltmeter
intermediate range voltmeter
very high range voltmeter

10. Potential transformer is similar in design to a _____
C.T.
Step up transformer
Power transformer
Step down transformer

11. The secondary winding of a P.T. is designed for ____
220 V
2.2 kV
1.1 kV
110 V

12. The primary current in a C.T. is _____
independent of secondary circuit
dependent on the secondary circuit
depends on the transformation ratio
depends on the nominal ratio

13. The excitation current of a C.T. ______
varies over a fixed range of operation
varies over a wide range of normal operation
is fixed over a range of operation
is fixed always

14. Secondary of a P.T. can be open circuited.
True
False
all of the above
None of the mentioned

15. When C.T. is connected in series with a line, a large voltage exists across the primary.
True
False
all of the above
None of the mentioned

16. Winding resistance of a P.T. can be reduced by ______
using thick conductors
decreasing the length of the winding
shorting the primary and secondary windings
using thin conductors

17. Leakage reactance is minimised by _____
using thin conductors
reducing leakage flux
increasing flux density
shorting the windings

18. High flux density is due to less turns.
True
False
all of the above
None of the mentioned

19. Ratio error in a P.T. depends on _____
secondary current
primary voltage
secondary current
turns ratio

20. In a P.T. values of components of currents are negligible.
True
False
all of the above
None of the mentioned

21. Ratio error can be minimised by _____
reducing the turns
reducing the current
increasing the voltage
using a good core material

22. Another method of eliminating the ratio error is _____
by reducing secondary turns
by increasing the primary turns
by increasing secondary turns
by reducing the primary turns

23. Increasing secondary burden _______
increases Is
decreases Is
keeps Is constant
decreases Ip

24. For a given Vp the Vs ___
increases
decreases
remains constant
depends on the supply

25. What is effect of the secondary burden on the ratio error?
ratio error is constant with secondary burden
ratio error decreases with secondary burden
ratio error increases with secondary burden
depends on the supply voltage

26. Vp is leading in phase, while Vs is lagging in phase.
True
False
all of the above
None of the mentioned

27. What is the effect of p.f. on secondary burden?
Ip shifts towards Io
Ip deviates from Io
Ip is independent of Io
Ip and Io cancel eachother

28. How is the transformation ratio dependent on the secondary burden?
decreases
increases
remains constant
depends on the supply

29. In a moving iron meter, the deflection torque is proportional to?
In a moving iron meter, the deflection torque is proportional to?
Current through the coil
Sine of measurand
The Square root of the measurand

30. The full-scale deflection current of an ammeter is 4 mA and its internal resistance is 400Ω. If this meter is to have a full deflection of 10 A, what is the value of the shunt resistance to be used?
49.99 Ω
0.16 Ω
1.5 Ω
2.6 Ω

31. The full-scale deflection current of a meter is 4 mA and its internal resistance is 400Ω. This meter is to have full deflection when 400 V is measured. What is the value of the series resistor to be used?
99.90 kΩ
100 kΩ
99.60 kΩ
100 Ω

32. Two ammeters, one with a full-scale current of 1 mA and internal resistance of 100 Ω and other a full-scale current of 10 mA and internal resistance of 25 Ω are in parallel. What is the total current, these two meters can carry without the reading out of scale in any meter?
1 mA
10 mA
11 mA
5 mA

33. A meter has a full scale of 90° at a current of 1 A. This meter has a perfect square law response. What is the current when the deflection angle is 45°?
0.5 A
0.25 A
0.707 A
0.67 A

34. The scale of a dynamometer type instrument marked in terms of RMS value would be_____
Uniform throughout
Non-uniform and crowded near the full scale
Non-uniform and crowded near the full scale
Non-uniform and crowded around mid-scale

35. Moving Iron Instrument can be used as _______
An ammeter for measuring DC as well as AC
For measuring DC current and voltages only
For measuring DC current and voltages only
For measuring AC current and voltages only

36. A 10 mA PMMC ammeter reads 4 mA in a circuit. Its bottom control spring snaps suddenly. The meter will now show ______
10 mA
8 mA
2 mA
Zero

37. The standardization of AC potentiometer is done by _____
Using a DC standard source and d’ Arsonval galvanometer
Using AC standard sources and transfer instruments
Using a standard AC voltage source
Using a DC standard source and transfer instruments

38. The inductance of a certain moving- iron ammeter is expressed as L = 10 + 3θ – θ24 μH, where θ is the deflection in radian from the zero position. The control spring torque is 25 × 10-6 Nm/rad. The meter carries a current of 5 A. What is the deflection?
2.4
2.0
1.2
1.0

39. A current of – 8 + 6sqrt{2} (sin (ωt + 30°)) A is passed through three meters. The respective readings (in ampere) will be?
8, 6 and 10
8, 6 and 8
– 8, 10 and 10
-8, 2 and 2

40. A rectifier type AC voltmeter consists of a series resistance R, an ideal full-wave rectifier bridge and a PMMC instrument. The internal resistance of the instrument is 100 Ω and a full- scale deflection is produced by a DC current of 1 mA. A voltage of 100 V (rms) is applied to the input terminals. The value of R required is?
63.56 Ω
89.83 Ω
89.83 kΩ
141.3 kΩ

41. A current of [2 + 2–√ sin (314t + 30) + 22–√ cos (952t +45)] is measured with a thermocouple type, 5A full scale, class 1 meter. The meter reading would lie in the range?
5 A ± 1 %
(2 + 32–√) A ± 1%
3 A ± 1.7 %
2 A ± 2.5 %

42. A moving iron ammeter produces a full-scale torque of 240 μN-m with a deflection of 120° at a current of 10 A. the rate of change of self-inductance (μH/rad) of the instrument at full scale is?
2.0 μH/rad
4.8 μH/rad
12.0 μH/rad
114.6 μH/rad

43. A moving coil of a meter has 250 turns and a length and depth of 40 mm and 30 mm respectively. It is positioned in a uniform radial flux density of 450 mT. The coil carries a current of 160 mA. The torque on the coil is?
0.0216 N-m
0.0456 N-m
0.1448 N-m
1 N-m

44. Two 100 μA full-scale PMMC meters are employed to construct a 10 V and a 100 V full-scale voltmeter. These meters will have figure of merit (sensitivities) as?
10 kΩ/V and 10 kΩ/V
100 kΩ/V and 10 kΩ/V
10 kΩ/V and 100 kΩ/V
10 kΩ/V and 1 kΩ/V

45. A PMMC rated as 100 μA is used in a rectifier type of instrument which uses full wave rectification. What is the sensitivity on sinusoidal AC?
4.5 kΩ/V
18 kΩ/V
10 kΩ/V
9 kΩ/V

46. The discharge of a capacitor through a ballistic galvanometer produces a damped frequency of 0.125 Hz and successive swings of 120, 96 and 76.8 mm. The damping ratio is?
0.0568
0.0887
0.0357
0.0441

47. The discharge of a capacitor through a ballistic galvanometer produces a damped frequency of 0.125 Hz and successive swings of 120, 96 and 76.8 mm. The logarithmic decrement is?
0.225
0.565
0.484
0.7887

48. Power is ______
rate of doing work
rate of producing voltage
rate of generating current
rate of overcoming friction

49. In A.C. circuits, power consumed is ________
product of voltage and current
it depends on the p.f. of the circuit in addition to voltage and current
it depends on the supply voltage
it depends on the magnitude of the circuit current

50. In D.C. circuits, power is measured using ________
ohmmeter and galvanometer
ohmmeter and voltmeter
ammeter and voltmeter
ammeter and galvanometer