Single-pole switch wiring diagram
Light: on
Flip the switch to open and close the hot. Tap a conductor to replay the current path. The copper highlight is the live path, not a wire colour.
A single-pole switch controls one light from one place by making and breaking the hot conductor. The supply feeds the switch, the switch passes the hot on to the fixture when it is closed, and the lamp returns on the neutral. Open the switch and the path is broken before the fixture, so the light goes out.
How this circuit works
There are three players: the hot coming in, the switched hot going out, and the neutral that completes every lighting circuit. The switch sits in the hot line. When its blade is closed there is an unbroken path from the supply, through the switch, to the lamp and back on the neutral, so current flows and the lamp lights. When the blade opens, that path is cut at the switch and no current can flow, so the lamp is dark.
Notice what the neutral does not do: it never gets switched. It is the standing return, always connected to the fixture, waiting for the hot side to be made. That is the pattern under nearly every lighting circuit you will meet — the neutral is a constant, and the switching all happens on the hot.
Where it goes from here
Master this and the rest follow. Add a second switch and two travellers and you have a 3-way. Feed the supply at the fixture instead of the switch and you have a switch loop. The single-pole is the seed all of them grow from.
Questions people ask
What makes a switch "single-pole"?
One pole means it opens and closes one conductor — the hot. It has a single moving blade with an on and an off position, so it controls a light from exactly one place. Everything more elaborate, from 3-ways to dimmers, is built on top of this idea.
Does the switch go on the hot or the neutral?
A light switch interrupts the ungrounded conductor — the hot — so the fixture is de-energized when the switch is off. Switching the neutral would turn the light off but leave the fixture live, which is the opposite of what you want. This diagram breaks the hot for that reason.
Why is the fixture still live at the lamp when the switch is off?
It is not, in this arrangement — the open switch sits before the lamp, so the whole fixture drops dead when the blade opens. Toggle the diagram off and watch the copper disappear from the fixture. That is exactly why the switch belongs on the hot side.
Related
- Switch loop wiring — same job, supply fed at the light instead.
- 3-way switch wiring diagram — control one light from two places.
- All wiring diagrams
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