What is the Operating Principles of Moving Coil Instrument?

The basic principle of moving iron instruments is it works on the principal of magnetic repulsion....

it consists of two irons one stationary n other fixed to a moving pointer

small current flows through a coil surrounding the irons.this creates a magnetic field ,which magnetise the two irons..

the magnetise iron will develop a repulsion force between each other, this will cause the pointer to move against the spring

the pointer stop moving when the spring tension equals the repulsion force between the magnets...