The Open Door Web Site
Electricity and Magnetism

The Laws of Electro-Magnetic Induction
.....

A

B

If no current can flow through the coil, it is not (visibly) affected by the moving magnet (diagram A).

If the coil is short circuited, a current can flow due to the induced emf and the coil is observed to be pushed away from the magnet (diagram B).

Similarly, if the magnet is moved the opposite way, the coil "tries" to follow it.

This observation illustrates Lenz’s law which states:

When electro-magnetic induction occurs, any induced current flows in such a way as to oppose the change producing it.

Lenz’s law is simply the law of conservation of energy applied to electro-magnetic induction.

 

© David Hoult 2008