Final answer:
A circuit has its own fuse or circuit breaker which act as automatic switches to protect against excessive current. Fuses have a low melting point and permanently break the connection when overheated, while circuit breakers can be reset and use a bimetallic strip to break the connection.
Step-by-step explanation:
In electrical circuits, each circuit has its own fuse or circuit breaker. Fuses and circuit breakers act like automatic switches that open when the sustained current exceeds desired limits.
A fuse has a metal strip with a low melting point that permanently breaks the connection of a circuit to a voltage source when it is overheated by an excessive current. On the other hand, a circuit breaker is an automatic but restorable electric switch that uses a bimetallic strip to bend and break the electrical connection at the points if overheated.