On Wed, 02 Apr 2008 10:45:08 +0100, Invisible <voi### [at] devnull> wrote:

>Right. So the potential difference between the terminals of a battery is 
>9 V, unless there happens to be a capacitor connected to them, in which 
>case the potential difference is magically 0 V despite the fact that a 
>vast current is being generated?

You are simplifying it to the extreme and using rigorous logic and
that does not work. A battery can be considered as a current source
with an internal resistance. N.B. we are talking dc here and not ac.
When you put a high impedance voltmeter across an open battery you
will get a reading of about 9.5 volts. This is the open circuit PD.
When you put a resistor across the battery it forms a resistor -
resistor circuit. When you put a cap across the terminals it forms a
R-C circuit. You would not normally do this as you should have a
limiting resistor in series with the capacitor. (And in real life a
shunt resistor across the capacitor to slowly discharge it when there
is no power applied) Also remember Michael was talking about
instantaneous voltages which are different from steady state ones
which are different again from ac. 
Or are you just having fun winding us up? :)

-- 

Regards
     Stephen

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