Saturday Science Sessions – Homopolar Motor

This Saturday Science Session is a simple DC motor using the basic principles of electricity and magnetism. All you need is a AA battery, a piece of copper wire (I used 14 gauge wire, but 16 or 18 gauge may work better), and a magnet!

Simply balance the negative terminal of the battery on the neodymium magnet. Then shape the copper wire such that it balances on the top of the positive terminal and the two bottom ends just hover around the magnet. You can check out the pics for details. And definitely try bending your copper wire into various shapes.

Both electricity and magnetism are caused by the movement of charged particles. If a wire is connected to a battery, the negatively charged electrons flow from the negative to the positive terminal of the battery. This current (the flow of electrons) produces a magnetic field.

Similarly, the atoms in a magnet are aligned such that the negatively charged electrons spin in the same direction. The area around the magnet where the force is active is called a magnetic field.

In this experiment, the copper wire attached to the positive terminal of the battery interacts with the magnet at the negative terminal, essentially completely a circuit that flows in the presence of the neodymium magnet’s field. The interaction of these two forces cause the wire to spin, a result of the Lorentz force! Any particles moving in the presence of an electric and a magnetic field produces a force, with an opposite reactive force.

As I write this, I’ve been watching my copper wire spin for 45 minutes and going strong!

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