It might help to realize that the fields are produced by charges which
accumulate on wire surfaces AND wherever there is a change in conductivity,
eg at resistor terminals.
-----Original Message-----
From: Paul Lulai
Sent: Friday, November 22, 2013 2:11 PM
To: Phys-L@Phys-L.org
Subject: [Phys-L] standard dc circuits
I have a question about the junction rule for simple dc circuits.
I have a battery connected to 1 lamp, then split to 2 lamps in parallel and
back to the battery.
For easy numbers, if 1 amp flows through the first lamp, then 0.5 amps flow
through each lamp in parallel (if all lamps are ideal).
Using the junction rule, I know that current into each junction or node must
equal the current out of each junction or node. It is simply a conservation
of charge in that area.
How does that reconcile with a fields approach? I might have some incorrect
notions below. I am open to correction.
The batteries produce a field that move charges already present in the wire.
If all wires are of the same material, diameter, length (and so on) why is
the current less in the parallel branches than in the wires before and after
the parallel branch? Does something make the field in the parallel branches
smaller than the field in the series portion before and after the parallel
branch? I don't see it.
Thanks for any input.
Paul.