PMMC Instrument MCQ

1. PMMC ammeter have uniform scale because

  1. of eddy current damping
  2. they are spring controlled
  3. their deflecting torque varies directly as current
  4. both spring controlled and having deflecting torque varies directly as current
Answer. d

2. PMMC meter is fitted in

  1. Ammeter
  2. Voltmeter
  3. Multimeter
  4. Wattmeter
Answer. c

3. In a PMMC instrument, the damping provided is

  1. Air damping
  2. Fluid damping
  3. Eddy current damping
  4. Magnetic damping using a magnet
Answer. c

4. Following are some facts related to PMMC instruments

  1. It measures only average values.
  2. Scale is linear
  3. Spring is used for controlling torque.
  4. Damping torque is usually provided by air friction damping.
  1. 1 and 3 are correct
  2. 1, 2, and 3 are correct
  3. 2 and 4 are correct
  4. 1, 2 and 4 are correct
Answer. b

5. Deflecting torque is _________ quantity under measurement in PMMC instruments.

  1. Directly proportional to
  2. Inversely proportional to
  3. Directly proportional to square of
  4. inversely proportional to square of
Answer. a

6. Moving coil (PMMC) and moving iron instruments can be distinguished by observing its

  1. Range
  2. Scale
  3. Size of terminals
  4. Pointer
Answer. b

7. Which of the following instruments has the highest torque/weight ratio among the given instruments?

  1. Attraction type MI instrument
  2. Repulsion type MI instrument
  3. Permanent magnet moving coil instrument
  4. Electrodynamometer instrument
Answer. c

8. Which one of the following is true about Permanent magnet moving coil instrument?

  1. It is cheaper
  2. It can be used for all frequencies
  3. It has no hysteresis losses
  4. It has lower torque/weight ratio
Answer. c

9. A moving coil instrument has a resistance of 10 ohms and gives full-scale deflection at 0.5V potential difference across it. How can it be adopted to measure a current upto 100A

  1. By connecting shunt resistance of 0.005 Ω
  2. By connecting shunt resistance of 0.05 Ω across the meter
  3. By connecting shunt resistance of  5 Ω across the meter
  4. By connecting shunt resistance of 10 Ω across the meter
Answer. a

10. Swamping resistance is used to compensate error due to

  1. Stray magnetic field
  2. Large supply voltage
  3. Large supply frequency
  4. Temperature variations
Answer. d

11. Moving coil instruments have which one of the following scales?

  1. Logarithmic scale
  2. Uniform scale
  3. Non-uniform scale
  4. Squared scale
Answer. b

12. Following is not an advantage of a permanent magnet moving coil instrument

  1. It has a uniform scale
  2. It can be used without error for a long period of time
  3. It has good damping torque
  4. Its range can be easily extended
Answer. b

13. A moving coil instrument, having coil resistance of 4.5 ohms gives a full-scale deflection of 30mA. The resistance connected in parallel with this instrument to read up to 2.5A is

  1. 6.46 Ω
  2. 0.0346 Ω
  3. 0.0546 Ω
  4. 0.0625 Ω
Answer. c

14. PMMC (D’Arsonval) is used for

  1. AC current
  2. DC voltage
  3. AC voltage
  4. All of the above
Answer. b

15. Two 100V full-scale PMMC type DC voltmeters having figure of merits (FOM) of 10 kΩ/V and 20kΩ/V are connected in series. The series combination can be used to measure a maximum DC voltage of

  1. 200 V
  2. 100 V
  3. 150 V
  4. 300 V
Answer. c

16. In PMMC instruments, damping is provided by

  1. The coil itself
  2. Separate pair of magnets
  3. An aluminium frame on which the coil is wound.
  4. Damping vane in an air tight chamber
Answer. c

17. In moving coil instuments, the ________ scale is used.

  1. Square
  2. Nonlinear
  3. Logarithmic
  4. Linear
Answer. d

18. A PMMC meter can be used as an ammeter using

  1. Series resistors
  2. Shunt inductors
  3. Shunt resistors
  4. Series inductors
Answer. c

19. A linear scale used in

  1. thermocouple meters
  2. moving iron meters
  3. hotwire meters
  4. moving coil meters
Answer. d

20. In a particular meter, the operating torque is directly proportional to the current passing through it, then the type of meter is

  1. moving coil
  2. moving iron
  3. electrostatic
  4. induction
Answer. a