How Your Circuit Breaker Works

At some point in our lives, we've all had issues with our electricity going out and inevitably we have to deal with locating and fixing a circuit breaker. The idea used to terrify me as a child because I did not understand it and thought it would probably electrocute me. Then it used to be a source of embarrassment because I hated to let my dad know that I did not even know how to fix it. As I grew older and moved out of my parents home to live on my own, it became essential to learn how to fix a lot of household items and features by myself. I am happy to say that all of the worry as a child could easily have been avoided if I had taken the time to learn how a circuit breaker works. So, here is a simple explanation of how a circuit breaker works so that you understand what you are doing when the power goes out.

Appreciate Your Circuit Breaker

First things first, be thankful for your circuit breaker. I know it sounds silly, but it is such a great device. Unless you work or live in an electric-free environment, then the place that you spend most of your time has a lot of electric current coming in. The circuit breaker is a safety device that cuts the power if too much current is coming into it. There would be fires a lot more often without them, so do not curse it if it cuts your power.

A Quick Tutorial in Household Electricity

To grasp what your circuit breaker does, you have to understand household electricity. Electricity is defined by three main attributes: voltage, current and resistance.

Voltage is what moves an electric charge. The current is the rate that the electric charge moves through a conductor. The conductor offers varying resistance to the flow depending on its size and shape. Current (l) = Voltage (v) / Resistance (r). Current, voltage and resistance are all relative to one another. If you increase the voltage, you increase the current. If you increase resistance, you decrease the current.

Electric charge moves from a power plant to your home using the power distribution grid, which is a fancy phrase that basically means all of those power lines and power substations you see every day but barely notice. The charge moves in a large circuit that is actually composed of many smaller circuits. One end (the hot wire) leads to the power plant and the other end (the neutral wire) leads to the ground. There is voltage along the circuit because one end connects to a high energy source (power plant) and the other end connects to a neutral energy source (ground).

Your house or office (assuming they have electricity), receive consistent voltage from the power plant through the power distribution grid. Resistance and current, however, varies. Appliances all offer a certain amount of resistance (referred to as load). The hot wire and the neutral wires should never touch and rarely do because the electric charge runs through appliances which act as resistors. Resistors in appliances limit the amount of charge that flows through a circuit. Appliances are designed to keep current at a low level because too much would heat the wires and cause fire.

Most of the time, this system works well. But every now and then, something happens that allows the hot wire to connect with the neutral wire. This can happen when appliances break or melt or when wires in the wall get punctured. If it were not for a circuit breaker, then whenever the hot wire connects with the neutral wire, a dangerous amount of charge could flow through the circuit because it would not reach any resistance.

That's where the circuit breaker comes in to save the day.

Enter Circuit Breaker

A simple circuit safety device is a fuse, which is simply a thin wire with a casing around it that plugs into the circuit. When a circuit is closed, the charge flows through the fuse wire. The fuse is designed to disintegrate when it gets too hot, which will cut off the circuit to the rest of your house or office wires before it causes severe damage.

A circuit breaker does the same thing; it cuts of the circuit when it gets too hot. The difference is that once a fuse disintegrates, you have to buy a new one and replace it. A circuit breaker can be used over and over again because it is basically a switch that can turn on and off.

A basic circuit breaker consists of a switch that is connected to either an electromagnet or a bimetallic strip.

Circuit Breaker with Electromagnet
When the switch is flipped to the on position, electricity flows through the circuit breaker terminals. The electricity magnetizes the electromagnet. The higher the current, the higher the magnetic force. The lower the current, the lower the magnetic force. When the current gets too strong and charges the electromagnet too much, the magnetic force pulls the switch towards it, which cuts off the circuit. The flow of electricity is then cut.

Circuit Breaker with Bimetallic Strip
A circuit breaker with a bimetallic strip works on the same principle, but instead of using an electromagnet, it uses a thin strip that bends when the current is too high. When the strip bends, the current is disconnected.

Other circuit breakers use an explosive charge that will ignite when the current is too high. The explosion will trigger a piston to flip the switch. There are also circuit breakers that measure current levels with electric devices, but they are more expensive and not used as often.

So, when your power goes out and your significant other tells you to go fix the circuit breaker, just flip the switch or plug in a new fuse. See, it really is not that difficult.