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Re: Polarized Plugs


If one believes that the wall socket is wired correctly, than
the grounding round pin of a three prong plug and the coomon of the plug
are the same. But devices with polarized plus usually are double insulated
and do not ground the case. The polarized plug is usually to put the
switch on the hot rather than the common wire. That way with the switch
off the case and and most everything is "safe" to touch. Also if there
is an insulation failure, the switch should help prevent latenight fires
cause by marginal failures. I think a number of small appliances can
fail and burn if the plug is reversed.

Roger Haar U of AZ physics


On Tue, 28 May 1996, Edwin R. Schweber wrote:

Hi all:

Can anyone explain why the newer appliance two prong plugs
are polarized so they can only be inserted into the outlet in
one orientation. I assume it has something to do with grounding,
but what does it accomplish that a three prong plug does not?

Thanks in advance

Ed Schweber