Magnet, coil and galvanometer: Observational Experiment

Aim

Devise a rule relating the existence of a current in the coil (as registered by the galvanometer) to the magnetic field through the coil.

Prior Knowledge

1. Magnetic field and field of a magnet.
2. Current.
3. Ideas about relative motion

Description of the Experiment

The set-up consists of a coil connected to a galvanometer and a magnet. The galvanometer is able to register how much current is flowing in the coil. The magnet and coil are moved relative to each other in various ways. Observe what happens to the needle of the galvanometer.

Addtional Information

Here is a simplified diagram of the magnetic field produced by a horseshoe magnet: It may help you to understand what is going on.

Youtube movies can be stepped frame by frame using the , and . keys on your keyboard. If you want to download the movie to your computer, right-click or control-click HERE.

Questions

1. Does it matter whether the coil is moving and the magnet is stationary, or if the coil is stationary and the magnet is moving?
2. Does movement of the coil relative to the magnet or visa versa account for the observation of non-zero current in all cases? If not, provide counter examples.
3. When neither the coil or the magnet are moving, is there any current in the coil?

Now devise a general rule which accounts for all of the observations so far.