Question

When the magnet as shown in the diagram, is moved towards the coil at a speed of 5 ms⁻¹, the galvanometer shows a certain deflection to the right.

How will the direction and magnitude of deflection change when the coil also moves with a speed of 5 ms⁻¹:

1. in the direction of the motion of the magnet?
2. in the opposite direction of the motion of the magnet?

Answer 1

The galvanometer’s deflection is dependent upon the rate of change of magnetic flux, which is influenced by the relative motion between the magnet and the coil.

1. The magnet and the coil travel in unison at the same velocity, resulting in no relative motion between them; hence, the magnetic flux through the coil remains constant. Therefore, no current is induced, and the galvanometer shows no deflection.
2. As the magnet and the coil move in opposite directions, their relative speed equals the sum of their individual speeds, resulting in a total of 10 m/s (5 + 5), which increases the rate of change of magnetic flux. Therefore, the direction of deflection remains the same (to the right), but the magnitude of deflection increases.