> Some kids latch on to the connection of Lenz's Law (the
> negative sign) and the chemistry class talking about LaChatlier's
> Principle.
At 09:17 AM 3/10/01 -0800, Bernard G. Cleyet & Nancy Ann Seese wrote:
CB's kids are correct? (a true analogy?)
It's a rather unhelpful analogy.
1) I've never been very much impressed by Le Chatelier's principle. When I
look at it, it seems to allege that
"Every equilibrium is a stable equilibrium"
... which just isn't true in general. Maybe it's "usually" true, but
counterexamples abound. For homework, find three common examples of
neutrally-stable equilibrium (no restoring force) and one common example of
negative stability (restoring force in the wrong direction).
It seems to me you can apply Le Chatelier's principle to system X if and
only if you already know system X is in stable equilibrium -- which is
circular and begs the question of how to find out whether system X is
actually in stable equilibrium.
2) In the case of Lenz's law, we have a pretty solid energy argument that
tells us far more about this system than Le Chatelier's principle ever could.