Re: Lenz's Law

[brian whatcott <inet@INTELLISYS.NET>]

At 09:40 3/22/00 -0500, you wrote:
> Can someone help me out and check my reasoning.
>
> Given: a long straight wire lying on a horizontal table carrying conventional
> current north.  Next to the wire, on the right, is a metal ring lying flat on
> the table.
>
> If the current in the wire is increased, there will be a growing B-field
inside
> the metal ring directed down into the table.  This should (I'm pretty sure)
> induce a counter-clockwise current in the ring which will cause a B-field
up out
> of the table in opposition to the change in field that induced the current in
> the first place (Lenz's Law?)
>
> What bothers me is that (by my understanding is that by Lenz's law) this
induced
> current in the ring should somehow oppose the increasing current in the wire,
> and I don't see the mechanism for that.  If the ring was part of a circuit
with
> resistance, the induce current would do work, which would mean that it would
> take more work to increase the current in the straight wire when the loop was
> present than without the loop.
>
> What mechanism would make increasing the straight wire current more difficult
> with the wire loop there?
>
> Stu Leinoff
> Adirondack Community College

The opposing current induced in the ring does work on the resistance
 of the ring - unless you propose that the ring is superconducting?


brian whatcott <inet@intellisys.net>
Altus OK