Why is one prong wider than the other? Polarization

	Nowadays, many two-prong devices have one prong wider than the
	other.  This is so that the device could rely (not guaranteed!)
	on one specific wire being neutral, and the other hot.
	This is particularly advantageous in light fixtures, where the
	the shell should neutral (safety), or other devices which want to
	have an approximate ground reference (ie: some radios).

	Most 2-prong extension cords have wide prongs too.

	This requires that you wire your outlets and plugs the right
	way around.  You want the wide prong to be neutral, and the
	narrow one hot.  Most outlets have a darker metal for the
	hot screw, and lighter coloured screw for the neutral.
	If not, you can usually figure out which is which by which
	prong the terminating screw connects to.