It is usually a white wire. The standard color for your hot wire is black.
Electrical Basics Wiring A Basic Single Pole Light Switch
How to identify wires in a light switch. The united states has strict codes relating to home wiring including clearly defined colors on the outer casing of the wires. Before undertaking any electrical project it is imperative that you know precisely what it is youre doing and to keep in mind that electricity can kill. The neutral from the source is connected directly to the neutral terminal on the light and the source hot is spliced with the white loop wire. For detailed step by step instructions on completing this home project. With that said this electrical tutorial presents a guide to identifying the switched live wire on a lighting circuit and also explains how to rewire a ceiling rose. Black means hot white signifies neutral and green indicates ground.
All wiring looks the same on the inside but the outside coverings come in different colors. If its not attached to your old switch look for a cluster of white wires bundled together in the back of your wall box. This circuit is wired with a 2 wire cable running from the light to the switch location. It is usually a white wire. The white wire is marked black on both ends to identify it as hot. The black wire is the hot wire which carries the electricity from the breaker panel into the switch or light source.
The white wire is the neutral wire which takes any unused electricity and current and sends them back to the breaker panel. If the person who installed the wiring followed regulations the house wiring colors should give away the identity of the hot and neutral wires. Color is usually the best way to identify electrical wiring. However if you need to rewire a light switch or a plug socket you may occasionally come across two black wires. This is usually only attached if your old switch is a smart switch or certain dimmer switches.