Electromagnetic Induction.
Prepare a circular coil out of copper wire.
Connect the two ends of this coil to the two
terminals of the sensitive Galvanometer with
the scale having "0" at the center.
This closed circuit is shown in the diagram.
Note that this circuit contains no source
of electricity and the Galvanometer shows
"0" reading initially.
Take a bar magnet "N" "S" and move it swiftly
towards the coil with the North pole facing
the coil.
You'll observe a deflection in the Galvanometer
when the magnet is moving.
The deflection indicates that current is set
up in the coil.
Now, move the magnet away from the coil.
The Galvanometer shows again a deflection
but in the opposite direction.
This means current is set up in the opposite
direction.
If you hold the magnet with its South pole
facing the coil, and repeat the above steps,
the deflections are again observed, but are
reversed.
Similarly, motion of the coil itself also
produces deflections in the Galvanometer.
When the magnet is kept stationary: Do you
observe any deflection when you just hold
the magnet stationary near the coil at rest?
No.
A relative motion of the magnet and a coil
induces the current in the coil.
The current produced by the relative motion
of the coil or the magnet is called an "Induced
Current" and is said to be set up by an induced
electromotive force (EMF).
The production of an induced EMF in a coil
in a closed circuit by the relative motion
of a magnet and the coil is called the phenomenon
of "Electromagnetic Induction."
