Lighting circuits

[Barncliff]

Can any electrician out there help me please.

In last two houses I have lived in I have had the same electrical problem(?):-

On the lighting circuit when I have taken the wire out of the lightswitch connection and with the other end unconnected I still find a small electrical current in the wire (as picked up by my electrical screwdriver). The main fuse box was still live at this point. On inspection of the cable, I can find no fault and suspect that the current I am finding could be inducted from running parallel to other live wires?

What prompted my question is that I've just taken off two wall lights while re-decorating (they worked fine). Just noticed the issue when looking to re-fit the lights and want to check this is safe before putting them back. Replacing the cable would be a very messy job.

Am I barking up the wrong tree or should I replace the cable anyway?

 

[electronicsuk]

Capacitive coupling and induction, if nearby cables are live and passing current then they can induce/couple a very small current into others around them. If you were to try and power any substantial load then the voltage at the end of the cable you're measuring should drop straight to zero. It doesn't take much to light a neon, and let's not even get started on the whole topic of *those* screwdrivers...

 

[Master of None]

Ha the old trusty neon screwdriver. I presume you mean small voltage? the current should be immeasurable. Don't worry a resident spark will be along in a minute.

edit. God damn electrosuk beet me to it.