Here we shall investigate a practical application of electromagnets. They can be used to make electric motors. First, using two permanent magnets, reinforce how like poles repel and opposite poles attract. In the diagram below, the two magnets on the ends are fixed and the one in the middle is free to spin around. Which way will the magnet in the middle spin?

It should spin clockwise until the North end of the free magnet is as close to the fixed South as it can be. At this time the South end of the free magnet is as close to the fixed North as it can be. If we were now able to switch the polarities of the free magnet we could get it to move again as the ends it faces will now repel each other.

If the free magnet is an electromagnet, we can switch its polarity by switching the direction of the electricity. This is how a motor works. As soon as the North and South ends of the free magnet get even with the oppositily poled fixed magnet, the polarity of the electromagnet is switched and it moves around again.

By using a slip ring, the direction of the electricity through the electromagnet can be changed every half rotation. Below is a sketch of a slip ring. Brushes or metal strips rub against the disk as it spins around. By doing this we can make it so the electromagnet is always being pushed and pulled, therefore always moving.

How could we make more mechanical energy?

-Stronger magnetic field

-Greater electrical current

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