Re: American and British (English)

On Sat, 16 Aug 2008 16:49:42 -0700, Hatunen <hatunen@xxxxxxx>
wrote:

On Sun, 17 Aug 2008 00:29:25 +0100, "Peter Duncanson (BrE)"
<mail@xxxxxxxxxxxxxxxxxx> wrote:

On Sat, 16 Aug 2008 15:55:17 -0700, Hatunen <hatunen@xxxxxxx>
wrote:

On Sat, 16 Aug 2008 23:37:47 +0100, "Peter Duncanson (BrE)"
<mail@xxxxxxxxxxxxxxxxxx> wrote:

On Sat, 16 Aug 2008 15:05:56 -0700, Hatunen <hatunen@xxxxxxx>
wrote:


Yes you can, but you cannot have current without voltage
difference.

Under normal circumstances. Take a conducting ring, poke a
varying magnetic field through the hole: current will flow
without a potential difference.

And if youc could find the voltage at two points on the ring, you
would find a voltage.

You can't find the voltage between any two points without
interfering with the current flow, thereby altering the
conditions by, for instance, diverting current out of the
magnetic field into a meter.

Any measurement interferes with the thing being measured. In the
case very small flows one uses a very high impdeance voltmeter to
minimise the interference.

Without such intervention the voltage between any two points is
zero.

So long as a current is flowing it cannot be; Ohm's Law is Ohm's
Law. There are complicating factors such as the inductance of the
ring. Remember you've postulated a varying magnetic field.

I postulated a varying magnetic field because only a varying
magnetic field will induce a current in a conductor.

Ohm's Law applies where current is created by the existence of a
voltage difference.

It does not apply in the same way when the current is created by
induction -- the presence of a varying magnetic field.

Perhaps someone else will follow this up. It's 1:36 am here and
I'm going to bed. I'll be back tomorrow.

P.S. Conventionally, electric current flows from positive to
negative. In the output coil of a generator or transformer it
flows in the opposite direction.

--
Peter Duncanson, UK
(in alt.usage.english)
.

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