Your home’s electrical system is divided into branch circuits. Each circuit supplies power to a different area of your home. Most household circuits are rated for 15 amps (20 amps for kitchen circuits). This means that the circuit can safely carry up to 15 (or 20) amps of current at one time. If you run multiple appliances at the same time on a single circuit, and their combined amps exceed the amperage rating of that circuit, the wiring will heat up. If the wire gets too hot, the insulation could melt, causing a shock or fire hazard.
Fuses and circuit breakers are devices added to circuits to prevent the circuits from overheating. A fuse is a round glass or porcelain plug-like device that screws into the main service panel. The fuse contains a thin strip of metal (zinc). If too much current flows through it, the metal strip melts, opening the circuit and stopping the flow of current. This is called “blowing a fuse.”
Newer homes contain circuit breakers instead of fuses. A circuit breaker is like a switch that opens (“breaks”) the circuit when it becomes overloaded. Each branch circuit in your home is protected by a different breaker switch. Like fuses, the circuit breaker switches are located on the main service panel.