The modern circuit breakers in a house or any building are the equivalent of the old-time fuses. Both fuse and circuit breakers are an absolute necessity, and represent one of the most important safety features in your home.
The idea of a circuit breaker is to cut the power to a circuit in the event of an overload. This acts as a safety device which neutralizes the circuit until an electrician can determine the cause of the overload. Without circuit breakers, the potential of an electrical fire is very high, as any piece of electrical apparatus connected to the circuit can cause an over-voltage situation.
To have a better appreciation of how these devices work, you should know a little about electricity, which has three specific attributes:
These elements can be thought of as water flowing through a pipe. Voltage is the pressure that makes the electricity move, current is the flow or the rate at which the voltage moves at any given point and resistance is friction, which decreases the pressure coming out of the other end. All of these elements are inter-related and when one changes, the other two change as well.
Circuit breakers at work:
The power that comes into your home is produced at a power plant, put into the grid and delivered to the homes of the power company’s customers. The electrical charge is connected to the hot terminal at the power plant, and the other line goes to ground. When this arrangement is not disturbed, power moves through the uninterrupted circuit, which is closed.
The source of your power, the grid, delivers electricity at a constant voltage, usually 120 or 240 volts, but the resistance varies in the consuming facility, say the house. Every house is distinct as they all have different appliances, which consume power, things like light bulbs, the TV, stove, etc. It is the resistance, also called load, which makes electrical appliances work. A toaster as an example has a filament which is made of a material which has a certain resistance to the charge, the charge has to work hard to move through the resistor, and hence it heats up, glows and makes toasted bread.
The hot wire and the ground wire never touch one another directly, the appliance that the wires are connected to acts as the resistor. It is the resistance of the appliance that limits the flow through the circuit carrying the electricity. Household appliances are purposely designed to operate at a low current for safety. If there is too much charge in the wire at any given time, the wires heat up and the potential of a fire exists.
The circuit breakers job is to cut the power to the circuit when the current goes beyond a certain limit; it does this by tripping and stopping the flow of power to the high resistance consumer.