# Magnetic Fields

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What is a magnetic field?
Region in which magnetic materials, or moving charges experience a force
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What magnetic flux density?
Measure of strength of the magnetic field, in Tesla.
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What is magnetic flux?
Φ = BA. Describes the magnetic field lines passing through a given area, Weber.
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When there are N turns in a coil, magnetic flux linkage = NΦ = BAN, Weber.
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What happens when there is a current through a wire?
Magnetic field is induced. Field lines form concentric rings around wire.
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How does an electromagnetic induction work?
Conducting material moves relative to a magnetic field. Electrons experience a force and build up on one side of the material. EMF is induced, as there is a potential difference. If connected to a closed circuit, current also induced.
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Magnitude of induced EMF is equal to the rate of change of flux linkage.
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What are the 4 factors affecting the EMF induced in a coil?
Number of turns (directly), magnetic flux density (directly), area (directly), time (inversely)
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How is an EMF induced in a second coil?
If the current through a wire changes, magnetic field changes. EMF induced in second coil, this is proportional to the change in current.
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What is the equation to do with mutual inductance?
Vs/Vp = Ns/Np, IsVs = IpVp
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What are the factors affecting EMF induced in second coil?
Magnetic flux density (directly), distance between coils (inversely), number of turns (directly), area of second coil in field (directly), time (inversely)
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What is Lenz's Law?
Direction of induced current/EMF is such as to oppose the change creating it
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How does Lenz's Law show the conservation of energy?
Ensures electrical energy gained by the induction of I/EMF is equal to an amount of energy removed from the system.
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## Other cards in this set

### Card 2

#### Front

What magnetic flux density?

#### Back

Measure of strength of the magnetic field, in Tesla.

### Card 3

#### Front

What is magnetic flux?

### Card 5

#### Front

What happens when there is a current through a wire?