Re: inductor circuit concept

[Bob Sciamanda <trebor@VELOCITY.NET>]

To directly address your concern:

> I want to write the loop theorem as:  -iR + L(di/dt) = 0
> as there is a potential drop across the resistor  and
> gain in the inductor.

During discharge the current is flowing in the positive direction but
falling in value; hence di/dt is negative and  - di/dt is positive, giving
the positive "gain" you expected.

Note that since we are choosing the direction of the discharge current as
positive, the term -iR will be numerically negative.  Since the current is
in the positive direction and falling in value, di/dt is negative.  Thus -iR
and + L(di/dt) could not sum to zero, but  -iR and  -L(di/dt) can sum to
zero.

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
www.velocity.net/~trebor