🚀 go-pugleaf

In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) writes:

>    I noticed long ago that if you (accidentally) touch a live
>conductor, there is an odd sensation reminicent of a rough surface.
>For example, I've noticed a short to a wall-switch faceplate recently
>by observing that if you touched the faceplate it had that
>"rough-ish" feel instead of feeling smooth (the feeling is kind
>of line a high-freq. vibration -- 60Hz?).

It is indeed the 60 Hz from the power source. The "rough" sensation you feel is
leakage current, well below 3.5 mA (probably in the neighbourhood of 500 uA), 
from the power source through your body to ground or lower potential level.

>You have to run your
>finger along to conductor to notice the sensation.  This feeling goes away
>when you cut the power, so it's not due to a real change in the
>surface of the conductor.

As you move your hand along the conductor you apply varying pressure on it
which will result in varying amounts of leakage current as the contact
resistance between you and the conductor increases or decreases.

It will go away when the power is removed, because the voltage differential 
which results in the leakage current is no longer available. If the sensation
remains after the power is removed, then the circuit is connected to some
device that will store energy (ie a coil or a capacitor)



-- 
Howard.Steel@Waterloo.NCR.COM  :-(  	I Think, Therefore I AM,
aka: Howard "The Duck" Steel   :-) 		I think