The disc of an instrument using eddy current damping should be of

The correct answer is option 1):(conducting and non-magnetic material )

Concept:

• Eddy current damping: When a conductor moves in a magnetic field an emf is induced in it and if a closed path is provided, a current (known as eddy current) flows This current interacts with the magnetic field to produce an electromagnet torque which opposes the motion
• This torque is proportional to the strength of the magnetic field and the current produced
• There are two common forms of damping devices:
  •  A metal former which carries the working coil of the instrument
  • A thin aluminium disc is attached to the moving system of the instrument, this disc moves in the field of a permanent magnet; The disc should be of conducting and non-magnetic material