Magnetism

Electric Motor.

I built this motor in a couple of lunch breaks at work, for somethihg to do.

The magnets were removed from an old SCSI hard drive. They are very powerful and probably made from neodymium-iron-boron.

In the next picture, the motor is running from two 1.5V 'D' cells. The current drawn is about 150mA.

Alternator.

This is a very simple but effective demonstration of electricity generation. A powerful (white) magnet is being rotated at 1300RPM by a pillar drill. A large (red) coil of wire is clamped in a drill vice and connected directly to a 3.5V lamp. The rotating magnetic field induces an alternating current in the coil, which lights the lamp.

This experiment is actually far more dangerous than it looks. Rare-earth magnets are very hard and brittle. If the magnet were to hit something, it would shatter, ejecting shrapnel at high velocity. If you decide to try this, wear goggles, ensure the magnet is well secured, reasonably balanced and is not run faster than about 1500 RPM. Switch off the drill before making any adjustments. Rotate the chuck by hand before switching on to ensure that the magnet will not hit anything. Use a magnet no more than 30mm across to limit the outside velocity (to less than 2.4 m/s).