May 18, 2010

The name of the sign.

Sometimes, a sign has a name.

There is a minus sign in the Maxwell-Faraday equation:

x E = - ∂B/∂t

That minus sign has a name, which is Lenz's Law.

Heinrich Lenz (1804-1865) wrote in 1833 that "An induced current is always in such a direction as to oppose the motion or change causing it."

The sign might be negative, but I look upon the Law as being positive. That is, in my opinion, Lenz's Law is a Good Thing. Because, otherwise, the electromagnetic universe would be profoundly unstable, with any perturbation resulting in positive feedback, amplification, and, ultimately, explosion!

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