Strangely specific question - if a poster whose username begins with a V got a small amount of hand lotion (from his hand) onto the electric prong of a household device, would that prevent current from conducting from the wall socket through the prong? There’s only so much that can be wiped off and a thin film would remain.
No.
The contacts are “wiping,” meaning that the metal slides across each half of the contact as it is inserted.
Unless the substance was dried onto the prongs, and very hard (epoxy?), it would get wiped away.
Yep.
There are special greases you can purchase that are designed to be applied to electrical contacts. They help reduce corrosion (including fretting corrosion). Furthermore, these greases are not electrically conductive; they’re a dielectric. As stated by beowulff, the wiping action of the contacts pushes the grease out of the way, thereby making a gas-tight seal between the contacts.
And the lotion is probably more likely to be a conductor than an insulator anyway.
Well, to an extent. It’ll be a much better conductor than air, but a much worse one than copper. Probably better than pure water, but worse than seawater.
I am not sure about hand lotions, but I would guess most are fairly good insulators. As mentioned, the greases that are designed to be applied to electrical contacts are dielectrics, and for good reason: a conductive grease could cause a short if it got between contacts that had a voltage across them.