How do 3 wire christmas lights work?

Just about the simplest circuit you can create uses just one battery and one light bulb. In one fun activity, you can give a person one wire, one battery and one light bulb. Ask the person to make the bulb shine. It's possible to get it to work, but it can still cause some trouble for people. read more

With the lights plugged in, use the voltage detector to check the live voltage wire between each light, starting at the end that plugs into the wall outlet. There should be voltage detected at the live wire going into the first light. read more