On Sun, 26 Oct 2008 21:39:27 -0700, marlboroman wrote:

Has anyone ever figured out why they put one wide and one narrow on a
plug that does not have a ground?

OK, I understand that on a lamp it's a good idea, or the socket shell
and bulb threads will be live if the hot side of the power line is
connected to that part of the socket.

But, lets say I have a all plastic cased electric power tool. (Like all
of them made in the last decade or more). I'm holding plastic, which
does not conduct electricity. It dont matter which side of the power
line goes to which side of the motor on AC. What's the point of having
that wide terminal? Is the only reason to **** off the user,
particularly those of us who are older and dont have the best eyesight
anymore. I cant see any other reason.....

My grinder does a quick job of narrowing that wide prong though !!! .

Short Answer: Lawyers and (product) Insurance.

Too Much Information (TMI) answer:

NEMA, National Electrical Manufacturing Association sets the standards
for all US Electrical plugs and receptacles. Search for a Wikipedia
write ups on NEMA standards. There are links at the bottom of the
Wikipedia to NEMA configuration charts. Your plugs are NEMA 1-15 type
plugs.

The National Fire Protection Association publishes the National
Electrical Code. The NFPA has adapted the NEMA standard as part of its
new building code for Electrical Safety. Many states adopt the NFPA
electrical code standards in their building code and statutes for
enforcement of such building codes.

Underwriters Laboratories, inc, the testing agency for Insurance
companies that issue policies against product liability, adopts the
National Electrical Code (which includes the NEMA standards) as part of
its product safety testing and check list.

Thus, in order to purchase product liability insurance a maker of
consumer products, like a homeowner's hand drill, needs to submit the
product to UL for safety testing. UL will give its blessing only
provided ...... (yada, yada, yada)

Thus the products you buy will have a narrow (hot or black wire) and a
wide blade (neutral or White wire indicated by the "W" on the NEMA 1-15
standard.) Even if the general public safety intent and need for the
narrow / wide blade makes no difference in a specific manufacturer's
product.