ICSE Class 10 Answered

The working of an electric bell is based on the magnetic effect of current. When the electric circuit is closed by pressing the switch K, the current flows through the coil CC and the core of electromagnet gets magnetized and therefore it attracts the armature A. Due to movement of the armature A, the hammer H strikes the gong G and the bell rings.

At the moment when the armature moves towards the electromagnet due to attraction, the connection between the strip SS and the screw S' breaks, which stops the flow of current in the circuit. So, the electromagnet loses magnetism and the armature A flies back to its original position due to the spring effect of strip SS. Now the armature again touches the screw S', resulting in the flow of current in the circuit. The electromagnet regains its magnetism and the armature A is again attracted, so the hammer h strikes the gong G again.

This process of make and break of the circuit goes on and the hammer strikes the gong repeatedly and the bell rings so long as the switch K is kept pressed.