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Re: induced emf again



I wrote:
| When E is equal to v × B, that
| is the condition for zero net force on the electrons. Any
| steady straight-line current meets this condition, whether
| the current is zero or not, and whether the resistance is
| zero or not.


Bob Sciamanda replied:

Yes the net force is zero, but if there is resistance one of the forces is
a retarding force. Consider the limit when this retarding force becomes
irresistible (the rod is an insulator). Then no charges move or
accumulate; no E is established; yet qVxB still operates - balanced
completely by the retarding force.

I agree with all that except the word "but". I don't see
how any of that is inconsistent with what I've been saying.

The retarding force must come from an E field, right?

I haven't seen the Lorentz force law written in terms of
q E + q v × B + retarding_forces
I think it's just
q E + q v × B

It may require extra effort to measure the E field associated
with an insulator, but it can be done. The following returns
over 250 hits:
http://www.google.com/search?q=electric+field-mill+measure