Circuit breaker

Figure 1: A diagram of a circuit breaker[1]

Circuit breakers are electrical safety devices that protect electric circuits from overload electric current conditions. They do the same job as fuses, but are not destroyed when activated. During overload conditions a circuit breaker will open the circuit to prevent overload, and potential damage, like fires. Circuit breakers contain a switch to return to the closed position after they have been flipped.

There are three main types of circuit breakers, they are listed in the table below.[2]

Circuit breaker type Description
Thermal Will respond to the excessive heat generating during overload current conditions.
Magnetic Will respond to the magnetic field generated during overload current conditions.
Thermo-magnetic Will respond to both the heat and magnetic field generated during overload current conditions. This is the circuit breaker equivalent to the slow blow fuse.

For Further Reading

For further information please see the related pages below:


  2. R.T. Paynter, “Basic Electric Components and Meters,” in Introduction to Electricity, 1rst ed. NJ: Prentice-Hall, 2011, ch. 3, sec. 3.6, pp. 98-107.