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: There's work, and then there's work



"Suppose we have a C = 1000 microF cap initially charged to Vo = 10 V
that is discharging through a small R = 10 ohm resistor and L = 20 cm
of copper wire with a diameter of d = 1.00 mm.

Using the density of copper (rho = 8.9 g/cm^3), the atomic mass of
copper (M = 64 g/mole), and the assumption of one conduction
electron per copper atom, we find a conduction electron number
density of n = (rho/M)*N_avog = 8.5 x 10^22 electrons/cm^3 and a
total of N = n(pi*d^2*L/4) = 1.3 x 10^16 conduction electrons."

Just a nit: I think the N is closer to 10^21 electrons in the wire.
Otherwise I very much appreciate the post.

Ouch! Thanks for the correction. I overlooked the fact that my n
was not in SI units.

I should have obtained N = 1.3 x 10^22 conduction electrons. That
changes my bottom line by a factor of one million (!!) without
changing my conclusions (!!!)

--
A. John Mallinckrodt http://www.csupomona.edu/~ajm
Professor of Physics mailto:ajm@csupomona.edu
Physics Department voice:909-869-4054
Cal Poly Pomona fax:909-869-5090
Pomona, CA 91768-4031 office:Building 8, Room 223