Aloysius Q Roger-YoMama wrote:
I live in a little house built in 1954. It has a certain number of
ungrounded receptacles.

In the context of DC power, I have some notion of the importance of
polarity.

For years, all small electrical devices/accessories (i.e. extension cords)
with 2-prong male plugs that I've seen have 1 wide and 1 thinner blade.
To facilitate connections and minimize hassle, I've been grinding the
wider to the width of the thinner blade.

This'll likely qualify as a "naive question". In the context of single-phase
power and small ~120v 60 hz AC ("Alternating Current") household devices,
what purpose does having 1 blade wider than the other serve?

Thanks,
AQ


The wider slot in those recepticals is (per code)connected to the
neutral feed conductor. That conductor is nominally at ground potential,
though it is not permitted to use it as a ground. Thus, touching that
conductor while also touching a grounded pipe will not electrocute you.

As one example, table lamps are (or should be) constructed so that the
conductor from the wide blade of the cord plug connects to the "shell"
of the bulb socket(s). That way, if you're changing a lightbulb in the
lamp, while standing on a wet concrete floor with bare feet, and your
fingers happen to touch the screw base of the bulb before it's fully out
of the socket, you won't get shocked.

There are numerous other examples of tools and appliances which take
advantage of the wide slot being at or extremely close to ground
potential, but the light bulb one is easiest to understand.

See:

http://home.comcast.net/~jwisnia18/jeff/screwing.gif

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.