A circuit breaker is a protective device that is
designed to open the circuit when a current
load is in excess of the rated breaker
capacity. If there is a short or other type of
overload condition in the circuit, the excessive
current will open the circuit between the circuit
breaker terminals. Two types of circuit
breakers are used.

Circuit Breaker: This type opens when
excessive current passes through it for a
period of time. It closes again after a few
seconds, and if the cause of the high current
is still present, it will open again. The circuit
breaker will continue to cycle open and closed
until the condition causing the high current is
removed.

Positive Temperature Coefficient (PTC)
Circuit Breaker: This type greatly increases its
resistance when excessive current passes
through it. The excessive current heats the
PTC device, as the device heats its resistance
increases. Eventually the resistance gets so
high that the circuit is effectively open. Unlike
the ordinary circuit breaker the PTC unit will
not reset until the circuit is opened, by
removing the voltage from its terminals. Once
the voltage is removed the circuit breaker will
re-close within a second or 2.
How A Circuit Breaker Works
Warning Lights