Date: Mon, 24 Oct 2011 14:38:14

Author: --- John Welch

Subject: Re: Image Current Demo

Post:

Yes, I was just drawing pictures to convince myself that the wire
should repel the plate if it were due to eddy currents:
http://cabrillo.edu/~jwelch/current.jpg
-John

Rueckner, Wolfgang wrote:
So what exactly is this "image current"? I just realized
it's not eddy currents because they would create a repulsion of the
current carrying wire, not attraction. If I had a similar copper bar
(rather than iron) next to the wire, I suppose I would get a repulsion?

On Oct 24, 2011, at 4:54 PM, Rueckner, Wolfgang wrote:

I'll bring my camera in tomorrow morning and take a
picture for you. I'll measure the resistance of the whole shebang and
calculate the current. My guess is 200 to 500 amps.

On Oct 24, 2011, at 4:51 PM, Adam Beehler wrote:

Well, there you have it.
Thanks, Wolf! Would you mind sending me a picture offline? How much
current do you estimate flows through your copper braided wire?

On 10/24/2011 2:25 PM, Rueckner, Wolfgang wrote:
I placed and iron bar (2"x4"x24") on the smooth cement
floor in our demo room and laid down our braided copper conductor (that
we use for repelling (or attracting) current carrying wires) next to
it. About 1" separation between iron bar and copper wire. Closed the
moose knife switch to short out our truck battery (just for half a
second, mind you) and the copper wire was attracted (and touched) the
iron bar. -- Wolf

On Oct 24, 2011, at 4:15 PM, Zani, Gerald wrote:

Wolf,

What did you use for a ferromagnetic plate and how did you arrange it?

How much did it move?

- Jerry

On Mon, Oct 24, 2011 at 4:09 PM,
Rueckner, Wolfgang
wrote:
Just
tried it. It works remarkably well!

On Oct 24, 2011, at 3:54 PM, Adam Beehler wrote:

> I have an instructor that tends to believe we ought to be able to
put
> together a demo showing "image currents." This is what he
proposed to
> me. Run a current-carrying wire along the surface of a
ferromagnetic
> plate/sheet. If the current is high enough, then there will be a
force
> between the current-carrying wire and its "image current" running
> parallel to it in the ferromagnetic surface just next to it. This
would
> need to be a whole lot of amps, like 500-1000!
>
> So...has anybody tried anything like this? Is there wire that can
> handle such currents for brief moments, yet not be so bulky that
the
> attractive forced created is outweighed by the wire's bulk? I need
>

--
Gerald Zani
Demonstration Manager
Physics
Brown University
(401) 863-3964

--
******************************
John Welch

Cabrillo College Physics Dept.

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