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MAGNETISM (Electromagnets (When a current flows through a wire, a magnetic…
MAGNETISM
Electromagnets
When a current flows through a wire, a magnetic field is produced and this can be proved using a compass
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Ways to increase magnetic field with a solenoid:
1 - increase current
2 - increase number of coils
3 - iron core (electromagnet)
The motor effect
When a magnetic field interacts with another magnetic field, causing the wire to experience a force in one direction
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Generator effect
When the potential difference changes direction as it moves in and out of the magnetic field, but if we have a complete circuit then the current is induced
An induced current and potential is given when the wire is kept still but the magnetic field is moved
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Electromagnetic devices
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A relay (used to turn circuits on and off safely):
the low voltage circuit contains an electromagnet and is safe to be switched on and off
in the high voltage circuit, the switch is replaced with 2 metal contacts and one is connected to a spring to keep them apart
*When the low voltage circuit is switched on, a current flows so there is a magnetic field. this attracts the iron block and causes the contacts to close and switch on the high voltage circuit.
The electric motor
When a wire is placed in a magnetic field, a force is experienced on both sides : left side is upwards, right side is downwards
There is a moment on both sides, so the loop rotates clockwise but when it is at 90* it will stop rotating and this is fixed by switching the direction of the current
A split - ring commutator is used and it is connected to conducting brushes to allow the current to pass onto the ring. the current produces a turning force on the motor and makes it rotate clockwise instead.
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