- Motors
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Objectives:
- To be able to explain how a motor works
Timing: 1 lesson
Motors are kind of generators in reverse. Name some everyday devices that have a motor in them.
Recall from last year the magnetic field pattern for a current-carrying wire, a square coil of wire or a solenoid.
Your teacher will demonstrate what happens to a current-carrying wire when it is passed through a magnetic field.
What you have just seen is called the motor effect. What happens if the direction of the current or magnetic field is reversed? Find out what Fleming's left hand rule is and how it predicts the direction of the force on the wire.
A simple DC motor consists of a coil of wire rotating in a magnetic field. What happens to the rotation if the current is increased, the no. of turns on the coil is increased or the strength of the magnetic field is increased? You should be able to answer these questions by playing with the model motors.
You need to know the different parts of a motor and what each bit does. What keeps the motor turning in the same direction? Use worksheet "The electric motor" to help you.
This type of simple motor is a bit too weak and feeble to turn anything much so practical motors have really curved magnetic poles which produce a radial field. This means the coil of wire can be attached to an axle which can then turn just about anything. There is a diagram at the bottom of: http://www.antonine-education.co.uk/.
You could do the following worksheet:
