Are there such things that allow quick changing which circuit powers outlets/lights

Question

Is there some kind of electrical switch that will take 2 different electrical circuits in and the load can alternate between circuits based on the position of the switch?

I was thinking about doing some extended electrical work, but I would like to maintain power to the downstream lights and outlets of that circuit. Yes, I could get an electrician to split the circuit, but a simple switch would be easier to DIY (and seems like a practical device).

Answer 1

You're over-thinking this. Get a replacement plug from the hardware store. Disconnect the "downstream" lights and put the plug on to that wire. Then use an extension cord.