[sdiy] Dr strange no volt!

[Ian Fritz]

At 04:26 PM 8/6/2004, M.A. Koot wrote:
>Interesting discussion, I've heard about having 0 volts and still having
>currents before, really weird.
>But when one does look at it straight to the point, Mister Ohm still says I
>= U/R.
>So no matter the resistance: if U = 0, I is also 0!
>Period. ;)

Sorry, that is not right.  Ohm's law does not apply to this situation 
(magnetic induction).  A closed loop of wire, even with finite resistance, 
will have an induced current in the presence of a changing magnetic 
field.  It will have the same potential (voltage) everywhere.  (Otherwise 
you would see a voltage increase every time you went around the loop.)  The 
current is driven by an internal "electromotive force". The energy 
dissipated I^2R is supplied by the work required to change the field.

You can learn about these simple and well-known phenomena in any elementary 
physics text.

   Ian