SS: Electric bell

The well-known application of electromagnet is the electric bell.

• When the ‘push’ switch is depressed, the circuit is closed. Current passes through the electromagnet windings and the core becomes magnetised.
• The magnetised core attracts the iron armature which makes the striker hits the gong.
• However, the movement of the armature opens the ‘make and break’ switch which switches the electromagnet off. The iron armature springs back to its original position, closing the ‘make and break’ switch and start the cycle again.

Notes:

• Soft iron is used to make electromagnets as it gains and loses magnetism quickly depending on existence of magnetic fields. The armature is also made of soft iron which can induce magnetism rapidly.
• No matter what direction is the current flow, the bell rings continuously as long as the ‘push’ switch is closed because any pole induces the armature.