Question

Figure shows a coil connected to a centre zero galvanometer G. The galvanometer shows a deflection to the right when the north pole N of a powerful magnet is moved to the right as shown.

1. Explain why the deflection occurs in the galvanometer.
2. State whether the current in the coil is clockwise or anticlockwise when viewed from the end \(P\).
3. State the observation in \(G\) when the coil is moved away from the north pole \(N\) of the magnet keeping the magnet stationary.
4. State the observation in \(G\) when both the coil and the magnet are moved to right at the same speed.

Answer 1

1. As the magnet moves relative to the coil, the magnetic flux linked with the coil changes. This induces an e.m.f. and current, causing the galvanometer to deflect.
2. The current is anticlockwise, viewed from the end of the coil facing the approaching north pole. This makes that end a north pole, opposing the magnet’s approach (Lenz’s law).
3. The galvanometer deflects in the opposite direction to its original deflection because the induced current reverses when the coil moves away.
4. There is no deflection: both move at the same speed in the same direction, so there is no relative motion and no change in magnetic flux.