Discussion of the Question 04/03
ELECTRIC OUTLET
The question was:
Electric outlet has two "current carrying holes", one of which is the
"phase" while the other one is "zero". (In addition, many outlets have a third hole
for the "ground".) After many years of usage with high-power devices (ovens, heaters, etc.)
one may notice that the "phase" side of the outlet shows some signs of overheating.
Sometimes (especially in low quality outlets or plugs, and in the cases when the plugs
are repeatedly inserted/removed from the outlets) burning signs can be detected
on the plug or the outlet. (These are more frequent in 220/230 Volt outlets.) Obviously,
the same current is flowing through both holes of the outlet. Why do
these signs appear on the "phase" hole/pin more frequently than on the "zero" side?
(6/03):
We got (25/5/2003) the following email from
Carlos Soria from Sevilla, Spain (e-mail
cshoyo@us.es):
Burning signs appear in the ''phase'' hole because a little spark is produced
each time something is plugged or unplugged, because there is a potential
difference between the ''phase'' and the plug, not present in the earthed side.
As the plug is approaching to the outlet, a electric field is forming, and
charge is being accumulated at both sides. The spark join these two 'electrodes'
carrying charge and weakening the electric field, that is to say, by generating
'displacement current' in the opposite direction. So, total current may be null
during the contact on the ''phase'' side and, consequently, on the earthed side,
with the difference that in the phase side spark conduction current is
liberating heat.
This could explain why phase side is burnt but not earthed side. Of course, the
higher the voltage, the stonger the effect.
(10/03):
We got (5/10/2003) an interesting email from
an anonymous correspondent (e-mail
al@alaweb.com). We do not think that this
email solves the problem, but nevertheless it is an interesting observation. Here
is what he wrote:
I had an oven that I plug and unplug often because the switch doesn't
work. The ground side is the side that is pitted. The answer is that if
you are right handed; you are going to put the plug in with the right side
going into the outlet first. The left side is the side which will draw the
arc and get pitted.
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