It serves as the second hot wire in the switch loop. In a 110 volt setup an additional wire usually red or blue normally indicates a hot wire controlled by a light switch.
The Cimple Co Cmp Scrw Mcro Blk 100p Electrical Wire Cable
What wire goes to the black screw. The ground wire goes to the green screw. The white wire goes to the white metal screws on an electrical outlet. The grounding wire is connected both to the switch using a pigtail wire and to the second cable run passing onward to the next switch. This means that there is a black hot wire a white neutral wire and a bare copper grounding wire. The black hot wire goes to the brass screw or into the hole in the back of the device on the same side as the brass screw. When you connect an outlet or light switch the black wire goes to the brass screws.
Under those conditions a black wire should be always hot and always on. The green or bare copper ground wire if the device has one attaches to the green screw terminal on the switch or to the electrical box. In typical american wiring the black wire on an outlet goes to the gold copper screw and the white wire goes to the silver screw. The ground wire goes to the green screw. The black wire from the new cable connects to the black hot wire in the fixture box and to one of the terminals on the single pole switch. At this first switch the black feed wire is connected to the common screw on the switch.
The white wire from the new cable connects to the fixtures hot wire terminal or hot wire lead and to the other screw terminal on the switch. The black hot wire this wire is fed from the circuit breaker to deliver power to the receptacle and it connects to the brass or bronze colored screw on the receptacle often labeled hot or live or black or red in some situations. This wire is sometimes red. Where do the white and.