A flat coil ABCD is freely suspended between the pole pieces of a U-shaped permanent magnet with the plane of coil parallel to the magnetic field.

(a) What happens when a current is passed in the coil?

(b) When will the coil come to rest?

(c) When will the couple acting on the coil be (i) maximum, (ii) minimum?

(d) Name an instrument which makes use of the principle stated above.

A coil ABCD mounted on an axle is placed between the poles N and S of a permanent magnet as shown in figure.

(a) In which direction will the coil begin to rotate when current is passed through the coil in direction ABCD by connecting a battery between the ends A and D of the coil?

(b) Why is a commutator necessary for the continuous rotation of coil?

(c) Complete the diagram with commutator, etc. for the flow of current in the coil.

In electromagnetic induction, energy transformation is from :

1. Electrical to mechanical
2. Mechanical to electrical
3. Electrical to chemical
4. None of the above

The magnitude of induced emf depends on the :

1. number of turns in the coil
2. rate of change of magnetic flux linked with each turn
3. current
4. Both (1) and (2)