Moving Iron Instrument MCQ

1. A moving iron instrument gives correct reading when used at

  1. Low frequency
  2. High frequency
  3. Only one frequency
  4. All frequencies to a certain value
Answer. c

2. Damping of deflecting type instruments is done to

  1. Reduce the oscillation of the pointer in the deflected position
  2. Make the moving system slow
  3. Make the moving system fast
  4. Reduce the angle of deflection of the pointer on the graduated scale
Answer. a

3. The damping force acts on the moving system of an indicating instrument only when it is

  1. Moving
  2. Stationary
  3. Near its full deflection
  4. Just starting to move
Answer. c

4. In case of over damping the instrument will become

  1. Oscillating
  2. Dead
  3. Fast and sensitive
  4. Slow and lethargic
Answer. d

5. In an attraction type moving iron instrument, the damping torque is usually provided by

  1. Air friction damping
  2. Eddy current damping
  3. Fluid friction damping
  4. Capacitive damping
Answer. a

6. The scale of moving iron (M.I) instrument is

  1. Uniform
  2. Cramped
  3. Linear
  4. All the above
Answer. b

7. In moving iron instruments, the iron moves in a direction to cause

  1. Coil inductance to be constant
  2. Mutual inductance to be constant
  3. Minimum reluctance path
  4. Decrease in the flux passing through it
Answer. c

8. If the current through the operating coil of a moving iron instrument is doubled, the operating force becomes

  1. One and a half times
  2. 2 times
  3. 3 times
  4. 4 times
Answer. d

9. Eddy current damping can not be used for moving iron instrument because

  1. The weight of the instrument will increase.
  2. The presence of permanent magnet required for this purpose will affect the deflection and the instrument reading.
  3. The size of the instrument will increase.
  4. Eddy current will pass through iron and thereby cause loss.
Answer. b

10. Scale of moving iron instruments is

  1. Linear
  2. Non-uniform
  3. Exponential
  4. Logarithmic
Answer. b

11. A spring controlled moving iron voltmeter draws a current of 1 mA for the full-scale value of 100 V. If it draws a current of 0.5 mA, the meter reading is

  1. 75 V
  2. 50 V
  3. 100 V
  4. 25 V
Answer. d

12. Deflection produced in moving iron instruments is

  1. inversely proportional to sqaure of rms value of operating current
  2. inversely proportional to rms value of operating current
  3. proportional to square of rms value of operating current
  4. proportional to rms value of operating current
Answer. c
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