The figure shows the structure of a circuit breaker. A circuit breaker is an automatic switch that cut off current in a circuit when the current become too large.
When the current in a circuit increases, the strength of the electromagnet will increase in accordance; this will pull the soft iron armature towards the electromagnet.
As a result, the spring pulls apart the contact and disconnects the circuit immediately, and the current stop to flow.
We can reconnect the circuit by using the reset button. The reset button can be pushed to bring the contact back to its original position to reconnect the circuit.