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Eddy current damping is provided in a moving coil instrument by

  • A.a light oil in which the moving system is immersed
  • B.a permanent magnet attracting the pointer towards zero
  • C.currents induced in the aluminium former carrying the coil
  • D.a vane moving in a closed air chamber behind the scale

Answer: C

The former moving in the strong field of the permanent magnet has currents induced in it whose reaction opposes the motion, which is both effective and free of any moving contact. Air vane damping is used where no such field is available.

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