On Tue, 07 Mar 2017 16:29:46 -0500, micky
wrote:

Why do laptop power supplies, the ones with black rectangular things in
the middle of the cord, have 3-prong plugs when everything you can touch
is plastic or "rubber"?

And, I believe, when there's nothing more dangerous than a lamp
underneath the plastic and the rubber? Less dangerous because some
light bulbs ger really hot!
If the power supply were to short power could get through the
laptop, and out the USB or headphone, or whatever jacks.?
Anyway, some require grounding by code, others don'r.