Read the page
on magnetism.
When a current
is passed through a wire which is suspended in a magnetic field, the wire
will move.
The direction
of movement is determined by the direction of the field and the direction
of the current.
The speed of
movement is determined by the strength of the field and the amplitude of
the current.
This principle
is used in the electric motor to produce rotation.
It is also used
in the loudspeaker where varying speech currents through a coil, suspended
in a magnetic field, causes movement of a cone, resulting in sound pressure
waves.
The moving coil
meter uses the same idea.
When the meter
is connected to a circuit, current passes through a coil.
The coil is
suspended in a magnetic field,and rotates when current passes through it.
A pointer fixed
to the coil indicates a value on a scale.
The Electric
Generator Principle is related.
Here a coil
is moved in a magnetic field.
This induces
voltages and current in the coil. |