Question

In the set up below, the suspended metre rule is in equilibrium balanced by the magnet and the weight shown. The iron core is fixed to the bench:

1. State and explain the effect on the metre rule when the switch S, is closed.
2. What would be the effect of reversing the battery terminals? 

Answer 1

1. The magnet will be attracted  towards the soft iron core.
   The end of the coil facing the magnet becomes South Pole when switch is closed; and the rule turns anticlockwise 
2. The polarities of the electro-magnet becomes reversed therefore the magnet is now repelled away from iron core ; and the rule turns clockwise