Question

A coil made of insulated copper is connected to a galvanometer. What will happen to the deflection of the galvanometer if this coil is moved towards a stationary bar magnet and then moved away from
it ? Give reasons for your answer and name the phenomenon involved.


CBSE Class X Science SA 2 (3 Marks)

Answer 1

When the coil is moved towards a stationary magnet, the magnetic field associated with the coil will change and so current will be induced in the coil. This will cause galvanometer to show deflection in one direction. Now,when the coil is moved away, the magnetic field will decrease and hence, current will be induced in the opposite direction causing the galvanometer to show opposite deflection. The phenomenon is called electromagnetic induction.

Answer 2

The magnetic field lines in space around the magnet caused by the bar magnet pass through  the coil.  As the amount of magnetic flux through the coil changes, because of the movement of the coil, electric current is induced in the coil turns.   This is indicated by the deflection of the galvanometer needle.

When the coil moves nearer to the magnet the deflection shows in one direction.  When the coil moves away from the magnet the deflection shows the other way from the middle 0, as the direction of the current in the coil reverses.

Phenomenon:  Farday's law of electromagnetic induction.