We know what each wire color performs in the circuit. The black wire is the "hot" wire, carrying power from the breaker panel to the switch or light source. The white wire serves as the "neutral" line, carrying any wasted power and current back to the breaker panel. Neutral must be intact for power to be restored after a circuit breakers tripped.
Electricity comes into your home in three-wire cables called "branches". One branch is the "hot" line or path carrying voltage from the street pole to your house. This path may pass through several appliances to get from the street pole to the wall socket that feeds it into your house. Each appliance on the hot path needs its own breaker installed by a qualified electrician. The other two paths are called "neutral" because they carry current but no voltage. These paths go from the breaker panel to the wiring closet or auxiliary panel, then out to the various outlets and lights plugged into them. If anything else plugs into an outlet on a live circuit, such as a hair dryer or vacuum cleaner, that would be an open circuit which would cause all power to be shut off from that house until the problem is fixed.
When you use electricity, it travels down its path, whether it's a hot path or neutral path, and turns on the desired appliances.
Black represents heat, white represents neutrality, and green represents ground. However, if you need to rewire a light switch or a plug socket, you may run across two black wires on occasion. Before you proceed, you must establish which black wire is hot. You do this by finding out which one causes the circuit to break when you touch it. If they're both live, then you'll have to replace them with only black wires.
Once you know which black wire is hot, you can find out what role it plays in the circuit by looking at the other black wires. They should be dead (not connected to anything) unless there's a problem with one of the other wires in the switch box or somewhere else in the building enclosure. If one of these other wires is live, it should be replaced too.
You should check all the black wires in case one of them was not properly cut off before it was soldered into place. It's possible that a black wire got cut too close to its insulation and some current might still be flowing through it even though it looks like it's dead. If this is the case, you will need to replace it.
Here's how to identify which black wire is hot: First, turn off the main power supply to your house at the breaker panel. This means removing the cover from the panel and closing the metal shutters attached to the panel box.
The white wire is neutral, whereas the other colors are heated. Electricians frequently use black, red, or blue wires to deliver electricity from the main panel to a circuit. Other colors, such as yellow or brown, may be used for switch wiring. Orange cables are commonly used to connect smoke alarms. The term "hot" means power; anything else connected to it that is not part of the power system is considered "neutral" or "returned" ground.
Heated appliances and equipment should never be wired directly from the line voltage provided by an electric company. This could cause serious injury or death if someone were to touch one of these wires while they're still hot. To protect against this danger, electric companies supply each house with two sets of wires: one set for live power (hot) and the other set for dead power (neutral and return). These three wires must be kept separate from each other at all times; if they are not, then either some or all of the wires could be exposed when work is being done on a household electrical system.
Electricians usually have one set of hands-free tools that can attach to both types of wires at once. These tools include fuse boxes, circuit breakers, and transformer plugs. Fuse boxes and circuit breakers protect homes by shutting off power to certain areas of town if a fire starts there.