The switch will have two or three wires connected to it: an incoming hot wire, which is black; a return wire, which takes the load to the fixture and can be black, red, or any other color except green; and, occasionally, a grounding wire, which is green or bare copper. If you're not sure which one is which, just follow the path of the power back to its source.
There are two types of switches: fixed and toggle. With a fixed switch, once you connect it up, that's how it stays. You won't be able to turn off a fixed switch from outside the box, but that doesn't matter if you need it always on or always off. A toggle switch allows for both on/off control from outside the box.
Fixed switches are very durable because they don't contain any moving parts. They usually last for decades without any maintenance other than cleaning the contacts periodically with non-conductive cleaner to prevent short circuits. Toggle switches are much more delicate and should only be used with external controls. However, they do allow for more customization by allowing each position to have a unique appearance.
Toggle switches are available in virtually all shapes and sizes and can cost as little as $0.50 each at low volume manufacturers. Higher quality versions may be twice or even five times that price. But don't worry about the cost when selecting a switch type; either one will work fine for most applications.
The black (hot) wire is connected to the brass screw or a hole on the rear of the device on the same side as the brass screw. This wire is occasionally red. If the device has one, the green or bare copper (ground) wire connects to the green screw terminal on the switch or to the electrical box. Otherwise, it's not necessary to connect the ground wire to any part of the system.
The red (neutral) wire goes to the white screw or hole on the opposite side from the brass screw. This wire is always included with new construction and can be used to supply electricity to other appliances such as lamps or heaters that are not directly controlled by the switch.
Old wiring systems used aluminum wire for both hot and neutral, so they would be color-coded blue and black. These days, most electricians use black and red wire because it's easier to work with and provides better protection against accidental contact with live power. However, some older appliances may still have aluminum hot and neutral wires, so check with an electrician before you start working on these projects.
There are three wires Your switch will be wired with three wires: a hot (black) wire, a neutral (white) wire, and a ground (copper) wire. Brass screws are used to secure the black and white wires. The black wire goes up into the wall box, the white wire goes down into the wall box, and the brass screw secures them both together.
The maximum number of wires that can be in a switch case is eight. Wire gauge determines how many conductors can be on a single wire. The term "conductor" means any material that carries a current. " So if you were to put two solid metal wires inside of a switch casing they would be considered conductors and could carry a current.
If you added another type of conductor to one of these switches it would no longer be considered a switch but a circuit breaker. For example, if you added an aluminum wire to connect two different locations inside your house together then this would be an extension of the circuit breaker panel and not a separate switch.
The actual number of wires in a switch case depends on the manufacturer and what options they choose to include. But as a general rule of thumb, most switches have wires between 14 and 16 inches in length which allows for enough space to connect them to the correct terminals on the wall plate or faceplate.