Electric motors
Electric motors use the forces produced by magnetic fields to produce a turning motion. If you put a length of wire in a magnetic field and pass a Direct current. through it (such as from a battery), the wire will move. This is called the motor effect.
To make a simple DC motor, you need:
- two bar magnets
- a coil of wire wrapped around something to support it
- an axle for the coil of wire to spin around
- two half rings (‘split rings’)
The two bar magnets are held so that the north pole of one magnet faces the south pole of the other magnet. The coil of wire is mounted in the gap between the two magnets. The split rings make electrical contact with the coil and reverse the current every half turn. When an electric current flows through the coil, a force is exerted on the coil, causing it to spin.
A simple DC motor
The diagram shows:
- the coil of wire has an electrical current running through it because it is connected to the cell
- this generates a magnetic field around the wire
- the current is turned on and off at the correct time so the magnetic field of the wire interacts with that of the two magnets
- this makes the coil rotate
The speed of the motor can be increased by:
- increasing the strength of the magnetic field
- increasing the current flowing through the coil
