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Electrical Wiring in the Home/Two black/white wires confuse me!

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Question
I wired porch lights outside of the kitchen sliding glass door, never messing with existing switch. there were two black wires that i attached to the one black wire on fixture, and two white to the white wire on fixture, then attached ground. When i Turned on the power, the lights came on (with switch in off position) and as soon as i flipped the switch the power went out at this location as well as in one bedroom further down in the house, and other outlet in the kitchen... what did I do wrong ?

Answer
Tenille,

It sounds like you have a "switch leg" issue. A switch leg is a speacial switching circuit. The two wires you have at the light don't use the black and white wires the same way. One of the wire is the feed. The black is the hot wire and the white is the neutral. Just the the two prongs on a lamp plug. Attach both of them and your light goes on. This is just like you have observed.

Now to the switch leg. This is a speacial wire. It goes from a light to a light switch. The switch leg intercepts the hot wire before it goes to the light. brings it to one side of the switch. When the switch is closed the switch leg bring the hot back to the light and the light turns on.  To do this the color code gets ingnored.

In your outside light  box you need to tie the hot black conductor to the white white conductor of the other wire. connect them with a wire nut and put them in the back of the box. The remaining black and white conductors get matched up to the black and white of the light.  

ELECTRICITY PATH WITH SWITCH LEG

Black(hot from panel)=> White (switch leg)=> one side of switch=> Switch On=> other side of switch=> Black(switch leg)=> Black of light=> Light bulb(light glows on)=> white of light=> white(the return to the panel.
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