DC motorsElectric 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 through it (such as from a battery), the wire will move. This is called the.To make a simple, 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 motorThe 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 rotateThe speed of the motor can be increased by:.
increasing the strength of the magnetic field. increasing the current flowing through the coil.
A bar magnet is positioned near a coil of wire as shown in Figure P20.23. What is the direction of the current in the resistor when the magnet is moved (a) to the left? (b) to the right?
Electromagnetic inductionA magnet and a coil of wire can be used to produce an electric current. A is produced when a magnet moves into a coil of wire.
This process is called. The direction of the induced voltage is reversed when the magnet is moved out of the coil again. It can also be reversed if the other pole of the magnet is moved into the coil.If the coil is part of a complete circuit then a current will be induced in the circuit.Notice that no voltage is induced when the magnet is still, even if it is inside the coil.To increase the induced voltage:. move the magnet faster. add more turns to the coil.
increase the strength of the magnet.