Table of contents | |
Magnetism | |
Electromagnetism | |
Electromagnets | |
The Electric Bell | |
The Relay | |
The Loudspeaker |
A magnet has two ‘poles’, North and South:
If two magnets are brought together, like poles will repel while opposite poles will attract:
The area around a magnet where the magnetic force can be experienced is called the magnetic field.
The magnetic field is strongest where the field lines are closest (at the poles):
The Earth also has a magnetic field:
Iron loses temporary magnetism easily, steel does not
The corkscrew rule can be used to find the direction of the field around a wire. The thumb points in the direction of the current and the fingers point in the direction of the field. Reversing the direction of the current will reverse the direction of the field.
A solenoid is a coil of insulated wire.
This produces a stronger magnetic field than a single wire:
The magnetic field around the solenoid is the same shape as the field around a bar magnet except it also passes through the middle of the solenoid.
The North and South poles are determined by the direction of current:
The advantage of using an electromagnet is that it can be turned on and off
The strength of an electromagnet can be increased by:
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