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Electromagnetism (Magnetic Fields (Like poles repel and unlike poles…
Electromagnetism
Magnetic Fields
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The magnetic field lines of a bar magnet curve around from the north pole of the bar magnet to the south pole
Induced magnetism is magnetism created in an unmagnetised magnetic material when the material is placed in a magnetic field
Stell is used instead of iron to make permanent magnets because stell does not lose its magnetism eaily but iron does
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The Motor Effect
The motor effect the force is increased if the current or the strength of the magnetic field or the length of the conductor is increased, and reversed if the direction of the current or the magnetic field is reversed.
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To calculate the force on a current-carrying conductor at right angles to the lines of a magnetic field use the equation F = B I l
The Generator Effect
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When a conductor crosses through the lines of a magnetic field, a potential difference difference is induced across the ends of the conductor
The faster a conductor crosses through the lines of a magnetic field the bigger is the induced potential diference. When a direct-current electromagnet is used it needs to be switched on or off to induce a potential difference.
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Transformer
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The size of alternating otential diference is increased by a step-up transformer and decreased by a step down transformer
A transformer works only with ac because a changing magnetic field is necessary to induce ac in the secondaary coil
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