Introduction

Unlike fuses, circuit breakers can be used over and over again. When a power surge is detected, the circuit breaker breaks the circuit and flips the switch. The user must then flip the switch back to make the circuit.
Circuit breakers are used more than fuses because they do not have to be replaced. When an overload occurs, a simple switch is flipped off and all that is required is for the switch to be flipped back to the on position.

Construction

Circuit Breakers are made of 5 main components; the frame, the operating mechanism, the arc extinguishers and contacts, the terminal connectors, and the trip elements.
The frame is often made out of plastic to act as an insulator. It houses all the other components. It also determines how much voltage and current can be used.
The operating mechanism is the switch used to make or break the circuit. The switch is designed to snap on or off so there is no inbetween state. When the circuit is tripped by a current that is too high, the switch switches to the off position.
The arc extinguisher extinguishes the arc between the two conductors when the circuit breaker is tripped.
The picture to the right is an arc extinguisher in action.
Terminal connectors are used to connect the circuit breaker to the circuit.
The trip element senses that there is a current overload and makes the circuit breaker break the circuit which switches the operating mechanism to the off position.

Electromagnet Trip Element

This type of trip element relies on the sensed flow of electricity to be powered. When there is an overload, the electromagnet is powered enough to trip a switch, breaking the circuit. The electromagnet cannot work when there is not an overload.

The Thermal Trip Element

This is a type of trip element that uses two different types of metal bonded together which expands at different temperatures. When a current too high passes through these two pieces of metal, they will be heated causing one type of metal to expand. Because they are bonded, they bend. This is used to trip a switch that breaks the circuit.
The time is takes to trip the switch depends on how high the temperature is.

Advanced Trip Elements

More advanced circuit breakers use electronic components to monitor the current. This is much more precise but a lot more expensive. For this reason, the above two methods are mainly used.