How Circuit Breakers Work

Electricity is measured in three ways: voltage, amperage and resistance.

Electricity Basics

10-amp Dorman Smith thermal-magnetic circuit breaker10-amp Dorman Smith thermal-magnetic circuit breaker
Voltage is the amount of electricity being "pushed" through a conductor (the wire), amperage is the number of moving electrons, and resistance is measured in Ohms and is literally the resistance the electricity is meeting, either by a piece of equipment, conductor thickness, or some other means. A circuit, at a minimum, needs a power source and a method of carrying the electricity from the power source to the equipment and then back (two wires). A circuit breaker is a device that measures and monitors the current flow across a circuit. If the current increases to a predetermined level, it will trip a switch, severing the flow of electricity past it.

Electricity is measured in three ways: voltage, amperage and resistance. Voltage is the amount of electricity being "pushed" through a conductor (the wire), amperage is the number of moving electrons, and resistance is measured in Ohms and is literally the resistance the electricity is meeting, either by a piece of equipment, conductor thickness, or some other means. A circuit, at a minimum, needs a power source and a method of carrying the electricity from the power source to the equipment and then back (two wires). A circuit breaker is a device that measures and monitors the current flow across a circuit. If the current increases to a predetermined level, it will trip a switch, severing the flow of electricity past it.

Components

10-amp Dorman Smith thermal-magnetic circuit breaker

A circuit breaker includes the following components: an actuator that is used to trip or reset the circuit breaker; an actuator which forces the contacts together or apart; contacts that allow current flow when together and disrupt current flow when separated (act as the "switch"); terminals; a bimetallic strip; a calibration screw; a solenoid; and an arc divider or extinguisher.

Types and Operation

The most common circuit breakers are the bi-metal thermal circuit breaker and the magnetic circuit breaker, or a combination of the two. The bi-metal thermal circuit breaker measures current flow by using two dissimilar metals, one of which expands when its temperature increases. The magnetic circuit breaker measures current flow through a magnetic field. As the magnetic field increases to a predetermined level, it becomes strong enough to move the mechanical linkage, which will trip a switch and disconnect the electricity. A magnetic circuit breaker can be immediately reset because as soon as it trips, the magnetic field is de-energized, essentially resetting the circuit breaker. The bi-metal thermal circuit breaker must be cooled before resetting it.

Ground Fault Interrupters (GFI)

The ground fault interrupter (GFI) is a modern circuit breaker that is incorporated into all new homes. The circuit breakers in your home are usually all centrally located at a circuit breaker panel. The ground fault interrupters are located throughout your home, typically incorporated into wall plugs. Using GFIs, the home is divided into "sections," protecting a series of outlets and/or equipment. Like a circuit breaker, the GFI will trip if there is an increase in current that is above a predetermined value. The reset switch on a GFI is on the outlet itself.

About the Author

Eric Duncan is a military veteran and a professional in the safety, travel and aviation industries. Duncan has been writing since 2002 for magazines, newspapers, local business literature and on such websites as Singletraks.com. He has earned his Bachelor of Science in professional aeronautics and his Master of Business Administration.