Final answer:
A service panel is an enclosure containing overcurrent protection devices like fuses and circuit breakers that protect multiple circuits by opening when the current exceeds set limits.
Step-by-step explanation:
A service panel is an enclosure containing overcurrent protection devices supplying multiple circuits. These devices, such as fuses and circuit breakers, act like automatic switches that open when sustained current exceeds desired limits, effectively interrupting excessive currents to prevent thermal hazards. Fuses are made of a metal strip with a low melting point and are designed to permanently break the connection of a circuit to a voltage source when overheated by an excessive current. In contrast, circuit breakers are restorable switches that can be reset. They incorporate a bimetallic strip that bends when overheated, triggering a mechanism to break the electrical connection and protect the circuit. Advanced protection devices such as a ground fault circuit interrupter (GFCI) protect against shock by quickly responding to changes in current flow, and an isolation transformer insulates the device being powered from the original source to prevent shock as well.