Read the page
on magnetism.
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. |