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Re: Ohm's 'law' & minus sign



Chuck Britton wrote:

Has anyone else run into the Pedagogical Position which requires
Ohm's Law to be written with a MINUS sign?!?!?!?!

The justification seems to parallel the addition of the minus sign
known as Lens' Law in the EMF = - d(phi)/dt equation.

I need to be convinced, one way or the other. If it is as 'arbitrary'
as the Lens' Law sign, I'm inclined to leave it OUT!!!

I remember this from some circuit theory texts - sorry, no longer in my
personal library. The idea is that the conventional current runs from
regions of high potential to low potential, giving delta V = -Ri. The
form of Ohm's law relating current density and field does not need the
negative sign because the conventional current density responds directly
to the field.

Bob at PC