All ground wires and device terminals are connected together in each outlet box.
In each electrical box, all ground wires are connected together. Ground is also connected to the ground terminal of a device (switch, receptacle, light fixture, etc).
Conventional Light Switch Wiring Diagram
Alternate (California Style) Light Switch Wiring Diagram
Switch terminal connections are interchangeable.
Another NM cable connects from this switch box to the light fixture box. Both 120 volts and neutral travel from the switch box to the light fixture box.
With alternate light switch wiring, an NM cable supplies 120 volts from the electrical panel to a light fixture outlet box.
Another NM cable connects from the light fixture box to the switch box. In the diagram below right, a 2-
The white wire carries 120 V, the black wire carries the switched 120 V. Since the white wire is hot, a black piece of electrical tape is placed on each end.
This alternate type of wiring is no longer allowed by the NEC as of 2011 if a neutral wire is not present inside each switch box.
Diagrams shown on this page are simplified for clarity. Electrical outlet boxes can have numerous NM cables going in and out. See Actual Switch Box Wiring.
Typical NM Ground Wire Connections Diagram is shown below.
Light Switch Wiring