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: Electrons



Two parts to the answer.

1. The current in a wire is proportional to the average drift speed of the
electrons. This is not their actual speed between collisions, but
actually a very slow speed that accounts for the fact that the electron
bounce randomly through a wire in all directions, with it being slightly
more probably to end up at the lower voltage at one end of the wire.

2. When a steady state situation is achieved, it is indeed the decrease in
average electron speed (and thus KE) that goes into heating up the
resistor (i.e. getting it's electrons and atoms to move more).

-------------------------------------------------------------------------
Rubin H Landau http://www.physics.orst.edu/~rubin/
Professor of Physics rubin@physics.orst.edu
499 Weniger Hall __o 541-737-1693
Oregon State University _ -\<,_ fax: 541-737-1683
Corvallis OR 97331 USA ...(_)/ (_) home: 541-752-4601
-------------------------------------------------------------------------

------------------
On Mon, 19 Apr 1999, David Abineri wrote:

How do you folks answer the following high school student question?

As electrons move through a circuit, say a battery and single resistor,
energy is given up in the resistor as perhaps, heat or light. Now, what
is different about these electrons after passing through the resistor
compared with before they entered the resistor? They are not moving more
slowly so it is not a kinetic energy situation so where does this heat
come from?

I find it to be the ultimate question if one is to understand what is
happening and I fumble around with the notion of falling through a
potential difference but then we get hung up on a mass that falls
through a height and the energy manifests itself as kinetic so the
metaphor breaks down.

How do (would) you guys answer this to a high school student?

Thanks, David Abineri

--
David Abineri dabineri@choice.net



-------------------------------------------------------------------------
Rubin H Landau http://www.physics.orst.edu/~rubin/
Professor of Physics rubin@physics.orst.edu
499 Weniger Hall __o 541-737-1693
Oregon State University _ -\<,_ fax: 541-737-1683
Corvallis OR 97331 USA ...(_)/ (_) home: 541-752-4601
-------------------------------------------------------------------------