Electrical Measurements MCQ Questions

1. A pointer of an instrument once deflected returns to zero position, when the current is removed, due to

(a) action of gravity
(b) mass of the pointer
(c) controlling torque
(d) damping torque

2. An instrument in which the value of electrical quantity to be measured can be determined from the deflection of the instrument, when it has been pre-calibrated by comparison with an absolute instrument is known as

(a) absolute instrument
(b) secondary instrument
(c) recording instrument
(d) integrating instrument

3. Damping torque in instruments is generally not produced

(a) pneumatically
(b) electro-magnetically
(c) electro-statically
(d) by fluid friction.

4. Which of the following materials will be preferred as a shunt for extending the range of measurement of a voltmeter?

(a) Copper
(b) Steel
(c) Aluminum
(d) Manganin.

5. Low temperature coefficient of the resistance used for extending the range of a voltmeter

(a) reduces inaccuracies due to the temperature variations
(b) enables instrument to work at high temperatures
(c) increases the least count of the instrument
(d) enlarges the scale of reading.

6. The deflecting torque in an instrument may be produced

(a) magnetically
(b) electrostatically
(c) thermally
(d) any of the above.

7. To take-care the change in frequency of AC current, while using moving iron type instruments,

(a) an induction coil is used
(b) a condenser of suitable value is used in series with the swamp resistance
(c) a condenser of suitable value is used in parallel with the swamp resistance
(d) a balancing circuit is provided.

8. A portable instrument is likely to have

(a) fluid friction damping
(b) pneumatic damping
(d) gravitational damping
(e) eddy-current damping.

9. In eddy-current damping systems, the disc is usually made of

(a) non-conducting and non-magnetic material
(b) non-conducting and magnetic material
(c) conducting and magnetic material
(d) conducting and non-magnetic material

10. Which type of wattmeter cannot be used for both AC and DC?

(a) dynamometer type
(b) electrostatic type
(c) induction type
(d) none of the above.

11. A moving iron type ammeter has few turns of thick wire so that

(a) resistance is less
(b) sensitivity is high
(c) damping is effective
(d) scale is large.

12. A repulsion type ammeter when used on AC circuits, reads

(a) peak value of current
(b) RMS value of current
(c) mean value of current
(d) equivalent DC value of current.

13. If damping torque is not provided in an instrument

(a) the instrument will show full wave of quantity even under small values
(b) the pointer will move only when full rated load is provided
(c) the pointer will oscillate about its final deflected position and will never come to rest even under steady conditions
(d) the pointer will oscillate about its final deflected position for quite time before coming to rest.

14. When the damping of an instrument is adjusted to enable the pointer to rise quickly to its deflected position without overshooting, in that case the instrument is said to be

(a) dead beat
(b) off beat
(c) over damped
(d) under damped.

15. When the damping force is more than the optimum, the instrument will become

(a) dead
(b) oscillating
(c) slow and lethargic
(d) fast and sensitive.

16. In a moving iron type ammeter, the coil has

(a) large number of turns of thick wire
(b) large number of turns of thin wire
(c) few turns of thin wire
(d) few turns of thick wire.

17. In a repulsion type instrument, the force of repulsion is approximately proportional to

(a) current
(b) square of the current
(c) inverse of the current
(d) inverse of the square of the current.

18. In moving iron type instruments because of the hysteresis in the iron parts of the moving system, the readings are

(a) higher on descending values but lower on ascending values
(b) higher on ascending values but lower on descending values
(c) higher on both ascending as well as descending values
(d) lower on both ascending as well as descending values

19. Magnetic shielding of the working parts is obtained by using

(a) anti-magnetic substance
(b) a wooden case for meters
(c) covering case of cast iron
(d) glass covers.

20. If the torque/weight ratio of an instrument is low, then it can be concluded that

(a) the meter will have uniform scale
(b) the meter will have non-uniform scale
(c) sensitivity of the meter will be high
(d) sensitivity of the meter will be low.

21. Which of the following cannot be described as the advantage of moving coil permanent magnet type instrument?

(a) they have uniform scale
(b) they have low torque/weight ratio
(c) they have efficient eddy current damping
(d) they have efficient eddy current damping

22. Which type of damping is generally preferred in case of instruments having weak magnetic field?

(a) air friction damping
(b) fluid friction damping
(c) eddy current damping
(d) hysteresis damping.

23. 132 kV AC voltage can be measured by

(a) moving iron voltmeter
(b) moving coil voltmeter
(c) hot wire voltmeter
(d) electro static voltmeter.

24. In which instruments the deflecting torque depends on frequency

(a) hot wire instruments
(b) moving coil instruments
(c) moving iron instruments
(d) induction type instruments.

25. On account of the effect of the inductance in pressure coil, the wattmeter at leading power factor tends to read

(a) low
(b) high
(c) normally
(d) erratically.

26. To measure the voltages and currents in the radio frequency range, suitable instrument is

(a) moving iron type
(b) moving coil type
(c) electro-thermic type
(d) electrostatic type.

27. When a 10 µF capacitor is connected across the terminals of an ohm meter, the instrument initially shows low resistance and then slowly the value of resistance rises to a very high value. What conclusion can be drawn about the condition of capacitor?

(a) the capacitor is faulty
(b) the capacitor is leaky
(c) the capacitor has some initial charge
(d) the capacitor is straight.

28. A permanent magnet moving coil type ammeter and a moving iron type ammeter are connected in series with the output of a half wave rectifier. If the moving iron type instrument reads 5 amperes then moving coil type instrument is likely to be

(a) zero
(b) 5 A
(c) 3.18 A
(d) 2.5 A

29. Thermocouples are generally used for accurate temperature measurements up to

(a) 100^oC
(b) 250^oC
(c) 500^oC
(d) 1600^oC

30. The commonly used material for thermocouple is

(a) Chromel-copel
(b) Chromel-alumel
(c) Platinum-rhodium
(d) any of the above.

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