[sdiy] Alternating dead current voltage??

[RMC]

> That is: Alternating Current Voltage!
> Why do we smear together the Current word and the Voltage word?

A voltage is the potenital difference due to flow of charge through a 
resistor, creating a difference in potential.

When you talk about AC voltages, you are discussing a voltage that is 
measured by an instrument that relies on a small current flow through it. 
For example, sticking a DVM across a mains supply gives you 240V rms or 110V 
rms etc. because you cause a very small current to flow in the meter and 
measure the difference in potential "seen" across some resistor or other 
inside themeter.

So, linking the "Current" with voltage makes physics sense.

A "potential difference" occurs when electric charge is separated and 
electric field exists as lines of force between those charges.  That's the 
subtle difference between a real voltage than can do work, and a difference 
in electric potential due to isolated charge (e.g. when you comb your hair 
on a dry day or you rub a balloon on your jumper - there's 10kV there but it 
won't kill you - a crude example).

> and in a superconducting device many strange things are possible!

True - but they still obey the laws of physics.

RMC, England