I have non-contact voltage detector that I use when I am working on electrical wiring. I have read that these devices work by measuring the electromagnetic field generated by the electricity in the wire. This makes sense to me in a circuit carrying electricity (for example, wire leading to a light bulb that is illuminated).
However, I noticed that the device appears to also indicate the presence of a field on an extension cord that has nothing plugged into the end of it — so there is the potential for electricity to flow, but the circuit is open, so it’s not actually flowing. I would think that would, in turn, mean that there should be no electromagnetic field. But that intuition seems to be wrong.
Why does the electromagnetic field seem to be there regardless of if electricity is actually flowing?
In: Physics
It’s an extension cord, so it’s probably AC electric. That means that the voltage is constantly changing on the wire–even if nothing’s plugged into the other end–and so an electrical field is generated.
Latest Answers