Re: inductor circuit concept

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Mon, 30 Apr 2001, SSHS KPHOX wrote:

> The -iR is easy as it is a potential drop in the direction of the current.
> The idea of calling the potential across the inductor as always -Ldi/dt
> when trasversing in the direction of the flow is far less intuitive. It is
> so clearly a potential gain in the decay circuit that I have a hard time
> writing a negative. It does work and I recognize the fact that the -di/dt
> makes the term positive ( which is how I made the derivation work in class
> on Friday) but it seems more like memorizing a rule than not.

I agree with you.  I think this may be a good example to think
about in the light of our recent discussions about "algorithms."
This is, for me, now an algorithm which I use even though in many
individual cases it is not at all "immediately obvious" what sign
should be used on purely conceptual grounds.  On the other hand, I
have great confidence using this algorithm and that confidence
stems from my memories of having more than once busted a gut to
make those critically important conceptual connections.

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm