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It is best if you read
the page on the Magnetism
first.
When a piece of wire is
moved through a magnetic
field, a voltage and
current is induced in
the wire.
The same effect is
obtained if the wire is
stationary and the field
is moved.
The direction of current
flow is determined by
the direction of the
field, and the direction
of the movement.
The amplitude of the
voltage is determined by
the rate at which the
wire cuts the lines of
force.
Increasing the density
of the field or
increasing the speed of
the wire therefore
increases the voltage.
This principle is used
in the electric
generator, where a coil
is rotated in a magnetic
field to generate
electricity.
It is also used in the
moving coil microphone,
where sound causes a
coil to vibrate in a
magnetic field,
generating voltages
which represent the
sound waves.
The Electric Motor
Principle is related.
It relies
on passing a current
through a wire in a
magnetic field to
provide movement.
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