This free wiring diagram shows a basic circuit breaker box with breakers. This wiring diagram shows how the electrical circuits are wired and grounded for house wiring. You will see how some types of cable will have a red wire, a black wire and a white wire. This is Romex 3 wire cable made for 240-volt applications as you can see below.
Some appliances need two 120-volt lines to run. That’s why the heavier cable will use both a black wire and a red wire as hot lines. The white wires will be neutral as usual. Both the red and black will attach to the breaker which is extra wide to cover two hot bus bars in the breaker box.
The big 1/0 gauge cables that come from the meter are Aluminum cables that resist heat really well. Two cables will connect to the hot bus bars and one cable will connect down to the neutral bus bar.
This wiring diagram shows a basic breaker box with breakers.
The picture of the breaker box shows different sizes of breaker fuses. The narrow breakers cover only one hot bus giving it 120-volts. The wide breakers cover two hot bus bars giving them 240-volts. That’s how the voltage differences work.
The amperage ratings of the breakers is a different kind of thing that works on current or Electric flow. They trip if there is over-current in the case of a short circuit.