Electrons move in a conductor very slowly. Far, far, below the speed of
light.

So, when you put a voltage or a source of electrons (which have charge and
eminate their own tiny electric field) at one end of a conductor, what
exactly propagates through the conductor, so that the voltage at
the end of the conductor appears (i.e. becomes measurable) in a
time suggesting propagation of the voltage (or charge) at near light speed?

Richard wrote:
Electrons move in a conductor very slowly. Far, far, below the speed
of light.

So, when you put a voltage or a source of electrons (which have charge
and eminate their own tiny electric field) at one end of a conductor,
what exactly propagates through the conductor, so that the voltage at
the end of the conductor appears (i.e. becomes measurable) in a time
suggesting propagation of the voltage (or charge) at near light speed?


Charge.

Put a row of marbles or ball bearings on a table. Roll another one so it
strikes the near end of the row, and notice that one leaves the far end
very quickly. A unit of momentum (a rolling ball) hits the near end, and
that unit of momentum propagates to the far end and appears in the form
of a rolling ball there, much more quickly than the balls themselves
roll. In this case, the momentum of the ball is propagating very quickly
from one end to the other.

Similarly, a unit of charge (analogous to the momentum of the rolling
ball) propagates much faster than the electrons. Put a unit of charge in
one end, and a unit of charge pops out the other at near the speed of
light, while the electrons themselves move at something like a few miles
per hour.

Roy Lewallen, W7EL

Roy Lewallen writes:

Similarly, a unit of charge (analogous to the momentum of the rolling
ball) propagates much faster than the electrons. Put a unit of charge
in one end, and a unit of charge pops out the other at near the speed
of light, while the electrons themselves move at something like a few
miles per hour.

Not only do electrons only move at a few miles per hour.
The electricity the power company makes us pay for is actually
alternating current. And that means that the same electrons are being
pushed into our house wiring, and then pulled out of it, over and over
again. And yet we have to pay as if the electricity were
new. Disgusing!

:-)

73 de LA4RT Jon

LA4RT Jon Kåre Hellan wrote:

Not only do electrons only move at a few miles per hour.
The electricity the power company makes us pay for is actually
alternating current. And that means that the same electrons are being
pushed into our house wiring, and then pulled out of it, over and over
again. And yet we have to pay as if the electricity were
new. Disgusing!

:-)

They must be charging us for the pushing rather than for the electrons.

Roy Lewallen, W7EL

LA4RT Jon Kåre Hellan wrote:

Not only do electrons only move at a few miles per hour.
The electricity the power company makes us pay for is actually
alternating current. And that means that the same electrons are being
pushed into our house wiring, and then pulled out of it, over and over
again. And yet we have to pay as if the electricity were
new. Disgusing!

Electrons DO move quickly in a conductor
but most of that motion is in random
directions. Electron drift, the motion
of particular electrons from one end of
a conductor to the other, is slow as
described.

FWIW, for most AC appliances and their
conductors, electron drift may be so
slow that electrons entering one side of
the plug never reach the other side
before a polarity reversal of the AC.

Chuck

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Roy Lewallen wrote:
Similarly, a unit of charge (analogous to the momentum of the rolling
ball) propagates much faster than the electrons. Put a unit of charge in
one end, and a unit of charge pops out the other at near the speed of
light, while the electrons themselves move at something like a few miles
per hour.

That works for DC steady-state. For DC transient-state,
photons come into play because the electrons have been
accelerated by the DC leading-edge step function. The
DC impulse during the transient-state is photonic
energy in action, i.e. electromagnetic wave action.

When a DC impulse is first applied to a transmission
line, the ratio of its E-field to H-field is fixed
at Z0 indicating that the energy transfer is photonic.
During DC steady-state the ratio of its E-field to
H-field is fixed by the load indicating that the energy
transfer is electronic.

For EM waves in free space or in a transmission line,
photonic generation and absorption never ceases because
the electrons are being continually accelerated and
decelerated. The cloud of photons is what transfers
most of the energy and the electronic analogy breaks
down.

It is a mistake to use a DC steady-state analogy for
EM waves. EM waves must obey a strict set of boundary
conditions including a ratio of E-field to H-field
that always depends upon the medium.
--
73, Cecil http://www.w5dxp.com

LA4RT Jon Kåre Hellan wrote:
Not only do electrons only move at a few miles per hour.
The electricity the power company makes us pay for is actually
alternating current. And that means that the same electrons are being
pushed into our house wiring, and then pulled out of it, over and over
again. And yet we have to pay as if the electricity were
new. Disgusing!

Well Jon, you can get the best of the power company
by pushing back. If you push back hard enough, your
KWH meter will run backwards. :-)
--
73, Cecil http://www.w5dxp.com