A model electric motor

This page shows a simple model DC electric motor that you can make in the laboratory.

Electric motors play a very large part in our everyday lives. Perhaps you have made an electric motor like the one shown in the diagram. You will find electric motors in CD players, sewing machines, electric drills, washing machines, hair driers etc.

An electric motor like the one above needs three things to make it work:
1. a magnetic field;
2. a coil of wire with a current flowing through it;
3. a means of getting this current in and out of the coil.

When a wire carrying a current is in a magnetic field there is a force on it at right angles to the field.
(See: Flemings left hand rule)

A coil in a magnetic field experiences an equal but opposite force on its two sides and so the coil twists.

If we start with the coil in the position shown in diagram (a) then there will be an upward force on side (1) of the coil and a downward force on side (2) of the coil.
The coil will therefore start to twist in an anticlockwise direction.
The inertia of the coil and core keeps it turning until the input wires make contact with the ends of the coil again (diagram (b).

This time the positive wire touches side (2) and the negative wire touches side (1).
Side (2) now moves up and side (1) moves down — the coil continues to turn in an anticlockwise direction.

This process then continues and so the coil spins.

schoolphysics: Simple electric motor animation animation

To see an animation of a simple electric motor click on the animation link.