Electromagnet Field Experiments

To prove or satisfy the postulating of laws which evolved from the work of two scientists.

First, Michael Faraday, 19th century chemist and physicist, discovered that a moving magnetic field affects a conductor and induces currents in that conductor.

Second, Heinrich Lenz, 19th century physicist, found that the induced currents in the conductor generate their own magnetic field, which oppose the direction of the magnetic field of the moving magnet.

Activity 1: Falling Magnet in a Copper Tube.

Take a copper tube (it’s conductive but non-magnetic) and drop a piece of steel down the tube. Yes, the piece of steel will fall through, and it falls close to the acceleration due to gravity.

Next, using the same copper tube, drop a magnet into it (a strong one such as a neodymium rare earth magnet works best). Notice the magnet now falls very slowly. This is due to the effect of Lenz’s Law - the induced current in the copper tube creates its own magnetic field opposing the magnetic field created by the magnet.

Activity 2: Arago's Swinging Magnet Experiment.

Another demonstration of magnetic induction is based on a simple experiment first proposed by Dominique Arago, a 19th century French scientist. The original experiment proceeds by hanging a magnet from a string over the surface of a conductive, but non-magnetic material such as copper or aluminum. Swing the magnet back and forth close to the surface but not touching. The magnet’s swing should be seen as dampened when the conductor is in close proximity.

Because the dampening effect is often very subtle, a better way to reveal the swinging magnet’s effect is to use an aluminum can placed on its side as the non-magnetic conductor. As a strong magnet is passed by the can a force will develop that starts to rock the can back and forth. Remember that a current is induced in a conductor (the aluminum can) in the presence of a moving magnetic field (the strong magnet). Lenz’s law holds that the current in the conductor generates its own magnetic field which opposes the moving magnetic field from the magnet moving.