Every electric circuit in a wiring system must be protected against overloads. An overload occurs when equipment is subjected to current above its rated capacity, that is, when the amount of current flowing through the circuit exceeds the rating of the protective devices, and this can cause damages.
For example, if a circuit is rated for 20 amps maximum, then a fuse or circuit breaker of that rating will be in that circuit. Then if the current exceeds 20 amps, the circuit breaker will create an opening, cutting off any more current flow.
