A lot of green apprentice electricians ask about how panels work, and more specifically what the roll of the circuit breaker is. Some guys think that breakers “put out” electricity, or that they “send” a certain amount of amperage to a load from the panel. This is not how it works.
To start out, an electrical panel is simply a place where all of the many loads throughout the house meet up with the main feeders or service entrance conductors coming into the building. It’s essentially a large junction box. But rather than just joining all of the branch circuits and feeders to the service entrance wires, we put breakers in between each circuit to protect that circuit from any problems that may arise.
To understand how electricity flows we must understand the idea of “difference of potential.” When a difference of potential energy exists between 2 wires, connecting those wires together will allow current to flow through them. It will be extremely dangerous due to the amount of electrons flowing through the circuit, and you will most likely see an explosion happen in front of you. So don’t do this. Electricity is extremely dangerous in a circuit without a load or impedance in it. So to make electricity useful, we have to introduce a load to the circuit. A load is essentially a resistance. It is something that slows current down. Loads can also be inductive/capacitive and therefore reactive rather than resistive, but we won’t get into the semantics of this topic, in this post. For now just understand that for electricity to be useful it must be slowed WAY down.
To read this entire in-depth article please visit http://www.electricianu.com/podcast/episode-17-how-circuit-breakers-and-electrical-panels-work