Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: EMF



For what it's worth:
Pedagogically, I always introduced the EMF(S) concept by describing the
mechanism of the linear electromagnetic generator. Here there are no
"mysteries". We can follow the entire mechanism in detail without
appealing to any chemical or quantum mechanical "mysteries". The charge
separation is initiated and maintained by the QVxB force. After the
transient build-up, inside the armature the force of the electrostatic
field of the separated charges is balanced by the QVxB force as the
carriers climb the PD hill. The work (per coulomb) done by the external
energy source is numerically equal to the PD established by the separated
charges, neglecting internal resistance.

Note that the Feynman lectures do much the same thing - EMF is introduced
via QVxB and Faraday's law in Vol II, para 16-1, as if chemical cells did
not exist. The chemical cell is given a hand-waving short shrift only at
the end of para. 22-3 of Vol II.

Let me emphasize that I consider the defining property of an EMF(S) in a
circuit to be that of an energy source for the current carriers as they
climb the PD hill (inside the EMF device) created by the separated
charges. The potential differences established, and measured, are the
result of charge separations maintained by the energy sources, EMF(S)s, in
the circuit.

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