Wiring a Light Switch - End of Circuit
The easiest place to wire a light switch is at the end of a circuit. This does not mean that you should plan all your circuits so that your light switches are necessarily at the end. A light in the middle of a circuit really isn't that much harder.
Before beginning any electrical work, it is wise to turn off the circuit and then to test to make certain that the circuit is indeed off with a circuit testing device. Circuits generally use either 12 or 14 gauge wire. In wire gauges, the bigger number designates a smaller diameter wire. As a rule of thumb you should use 12 gauge wire for 20 amp circuits and 14 gauge wire for 15 amp switches.
When placing the switch boxes, be sure to choose an easily accessible spot near the door about hand height. If you are in doubt as to where this should be, examine the positioning of other switches in your house. If you haven't any installed yet, 45 to 48 inches from the floor should work about right. It is best to make them all about the same.
In our diagram the source of power comes through the switch box. The black wire, which is the "hot" wire leads directly to the bottom connector on the switch. The switch, of course, should be oriented so that the "on" position is up and the "off" position is down. On most switches there are two ways to connect the wire to the switch. There are two little holes in the back of the switch as well as two screws on the side. You can either push the stripped wire (About 1/2 inch of the insulation can be removed with a wire stripper or more laboriously with a utility knife.) into the hole or curve it into a hook with a pair of pliers, wrap it around the appropriate screw and then tighten the screw.
Meanwhile, you should have set up the box for the light and run a wire between the two boxes. The white wire from the source is connected to the white wire from the light. Our diagram shows a ground wire connection (usually bare or green) directly to the box. This is only necessary on a metal box. On a plastic box merely connect all of the ground wires together. Take the black (hot) wire that leads from the light and connect it to the top connector on the switch. Now twist the white wires together and use a cap or electrical tape to insulate the splice.
In the light box, connect the black and white wires to the light, this will generally be a fairly obvious process as most lights come with both black and white wires as well as a ground connection. If the light is one of the simpler ones, you can generally distinguish between the connectors, one will usually be made of wire that is silver in color, the other will be vaguely brass. The ground wire can be hooked directly to a metal box or to a connection on the light itself. Sometimes there will be a green wire.
Generally, it is wise to test your light before screwing the switch into the wall or the light into the ceiling. Test again after all the components are made secure.
If you are in any way confused by this explanation, please refer to our diagram.