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Magnetism (Electromagnetism (A current produces a magnetic field…
Magnetism
Electromagnetism
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Right-hand grip rule shows direction of current
–> thumb points in direction of current
–> fingers give direction of field
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Uses: relay switches, electric bells
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Loudspeaker:
Motor effect: an alternating current from a signal generator causes a changing magnetic field in a coil of wire
This is repelled and attracted very quickly from a permanent magnet which moves the diaphragm back and forth
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DC Motor
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At 180°the commuator contacts switch over ensuring the current continues to create a torque in the same direction and the motor continues to turn
Two types of magnet
Hard: retains its magnetism for a long time (eg. some steels) and is suitable for making a permanent magnet
Soft: magnetic material quickly loses its useful magnetism (eg. iron) and is suitable as the core of an electromagnet