How do you wire a new light with an on off switch using wires coming from another light?

Answer 1

If you have unswitched supply from a light you need to route the supply through the new switch to the new light. You want to switch the black wire and just connect the white wires together with a wirenut and connect the bare ground wires together by a separate wirenut.

Answer 2

You can wire the new light by connecting the wires from the existing light fixture to the new light fixture. You would connect the hot wire (typically black) to the hot terminal on the new fixture, the neutral wire (typically white) to the neutral terminal, and the ground wire (typically green or bare copper) to the ground terminal. You can then install the on/off switch in the circuit to control the power to both lights.

Answer 3

You can extend the wiring serving a light fixture only if your new light is to be controlled by the existing switch.

If you are adding a new switch for the new light you can extend the branch circuit serving another light by connecting to it anywhere before the switch, most obviously at the box where the switch is. If the existing light has multiple switches, you need to locate the one with the power feed.

NB for every electical box you will see a marked volume. You can only add wires or devices to a box if the box has sufficient volume to add more wires ir devices. You may need to consult the electrical code or a handbook. If you add the new light switch by replacing the existing switch box with a wider box, you'll be fine. If you are tapping in to the wiring and putting your switch in a different box, or you are putting in one of the devices that has 2 switches on 1 strap, then it depends on the box and what's already in it, but you may have to replace it with a deeper box that has more wiring volume.

Always remember to turn off the power at the circuit breaker or fuse box before opening any existing circuit boxes, even if you're "just looking".