Re: [Phys-L] [**External**] Lenz's law
I don't know that this is an answer that has been approved here in the
past...but it seems to me that if you could change the minus sign (and
nothing else!) then your various experiments would all violate conservation
of energy. Motors would have helping EMF rather than back emf. Generators
would become easier to turn as the current increased -- you could even let
go and let the force on the electromagnetically induced current take over
for you!
So I would say that Lenz's law is consistent with the law of conservation
of energy. But as I said, I think others will disagree... :)
On Thu, Apr 25, 2024 at 1:09 PM pschoch via Phys-l <phys-l@mail.phys-l.org>
wrote:
>
> So, here's where I get myself into trouble. I encourage my students to
> understand why things happen, what causes them, and not just memorize the
> formulas. And now we've gotten to Induction -- Lenz's law.
>
> The textbook shows them that the induced EMF opposes the change causing
> it, thus the negative sign -- experimentally. Now I've had a student ask
> me what the underlying physical principle is that results in the negative
> sign. Honestly, I don't think I understand this well enough to give an
> explanation.
>
> Any help would be appreciated,
> Peter Schoch
>
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