Circuit breakers differ from fuses in that they are reusable. Circuit breakers open when the flow of current exceeds specified value and will close after a few seconds when current flow returns to normal. Circuits breakers are used due to the fact that they must operate at times under prolonged high current flow due to demand even though there is not malfunction in the circuit.
There are 2 types of circuit breakers. The first type opens when high current flow is detected. A few seconds after the excessive current flow has been removed, the circuit breaker will close. If the high current flow is experienced again, the circuit will open again.
The second type is referred to as the Positive Temperature Coefficient (PTC) circuit breaker. When excessive current flow passes through the PTC circuit breaker, the circuit is not opened but its resistance increases. As the device heats ups with the increase in current flow, the resistance increases to the point where the circuit is effectively open. Unlike other circuit breakers, the PTC circuit breaker will not reset until the circuit is opened, removing voltage from the terminals. Once the voltage is removed, the circuit breaker will re-close within a few seconds.