12 Dec
2001
12 Dec
'01
2:03 p.m.
If the speed of an electron in a wire is equal to the speed of light (IIRC,
it's slower than light), then an electron will travel about 11.80 inches in
one nanosecond, which is the point Hooper was trying to illustrate.
-----Original Message-----
From: Geoff Reed [mailto:geoffr@zipcon.net]
Sent: Wednesday, December 12, 2001 1:45 PM
To: classiccmp(a)classiccmp.org
Subject: Re: RIP: Betty Holberton
12 inch copper wire IIRC for MS
<snip>
12 Dec
12 Dec
3:26 p.m.
If the speed of an electron in a wire is equal to the
speed of light (IIRC,
it's slower than light), then an electron will travel about 11.80 inches in
one nanosecond, which is the point Hooper was trying to illustrate.
It's the electric field that propogates, moving electrons are a side effect.
The average speed free electrons in wire is such that they essentially never
get from one end to the other.
Eric
4:02 p.m.
On Wed, 12 Dec 2001, Feldman, Robert wrote:
If the speed of an electron in a wire is equal to the
speed of light (IIRC,
it's slower than light), then an electron will travel about 11.80 inches in
one nanosecond, which is the point Hooper was trying to illustrate.
I was always of the impression that the electrons themselves move slower,
but the propogation of waves in the magnetic field of a stream of moving
electrons was 2/3 the speed of light (roughly)?
Peace... Sridhar
5:09 p.m.
I was always of the impression that the electrons
themselves move slower,
but the propogation of waves in the magnetic field of a stream of moving
electrons was 2/3 the speed of light (roughly)?
The actual propogation velocity depends upon the geometry of the situation.
In some situations (like in coaxial cable, a well analyzed PC board, a well
modeled chip) the propogation velocity can be well determined. In a random
wire among a tangle of others you take your chances. 1/3-2/3c is usual.
Lower and higher velocities are possible.
Electrons are very much (billions of times) slower. Calculating the average
speed of an electron is easy and is left as an excercise for the reader, as
is explaining why, for a given current, electrons in a resistor generally
travel faster than electrons in a wire.
Eric
5:12 p.m.
New subject: Nanoseconds per foot (RE: RIP: Betty Holberton)
Boatman on the River of Suck <vance(a)ikickass.org>rg>:
I was always of the impression that the electrons
themselves move slower,
but the propogation of waves in the magnetic field of a stream of moving
electrons was 2/3 the speed of light (roughly)?
It depends on the geometry of the conductors involved;
the more inductance and capacitance, the slower the
signal travels. I seem to remember hearing a figure
of about 1/3 c for typical coax or twisted pair
arrangements.
Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury, | A citizen of NewZealandCorp, a |
Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. |
greg(a)cosc.canterbury.ac.nz +--------------------------------------+
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greg＠cosc.canterbury.ac.nz -
korpela＠ssl.berkeley.edu -
Robert_Feldman＠jdedwards.com -
vance＠ikickass.org