# Principles Behind the Operation of Electric Motors and Generators

Updated on October 20, 2012

## How do they work?

Electric motors are machines that convert electricity to mechanical energy. Electric generators are the opposite. They convert mechanical energy to electricity. These two are very common because the principles behind their operation are the same.

Electric motors and generators are composed of a coil, a magnet and a shaft. The magnet is attached to the shaft and the coil is placed in such a way that it will surround the magnet. The coil is often times wrapped around a metal to make the magnetic field stronger.

For electric motors, electricity is allowed to pass through the coil. This will create a magnetic field opposite to that of the magnet. The interaction of forces will cause the shaft to rotate. The strength of the magnetic field will determine the rotation speed of the shaft.

Electric generators work in reverse. Mechanical energy is applied to the shaft – it is rotated. This will cause an interaction with the coil and the magnetic field. Faraday’s law states that when a coil is allowed to move through a magnetic field, electric current is induced in through the coil. The current produced depends on the strength of the magnetic field and the speed of rotation of the shaft. The type of electricity, alternating or direct current, produced depends on the set up of the generator. Also motors made for direct current cannot work with alternating current and motors made for alternating current cannot work with direct current.

In reality, electric motors and generators are just the same. It just depends on the set up. Try tinkering with your desk fan. Remove the casing and solder out the capacitor – the square battery like looking thing near the motor, then connect the wires. Apply kinetic motion to the fan by making it rotate. Then use a multi-meter to check the plug for current. You’ll see that there will be a current reading. It will be small because of the weak kinetic energy you applied. And yes, you can transform your fan into a wind-powered generator.