One of the issues we dealt with last time was which way a galvanometer needle deflected when some change was made in a system consisting of a coil and a bar magnet. One of the questions to consider was what happened when the north pole of the bar magnet was placed near the right end of the coil and the area of the coil was increased.

Most of us came to the conclusion that the needle deflects in the same way as when the north pole is moved closer to the right end of the coil. What actually happens depends on a number of factors, including:

• the shape of the magnet
• where the magnet is relative to the coil
• the initial radius of the coil
• the final radius of the coil

Increasing the area of the coil can either increase or decrease the flux through the coil.