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Re: AC electricity in CA



SSHS KPHOX wrote:

I was listening to NPR on the way home and the lead in to the power crisis
said that they were not enough electrons to go around....I think that is
what I heard but the story did not repeat the claim! Ah well.

This bit of physics-abusive poetic license also has been spotted in at
least one California newspaper. We've survived "energy" shortages in
one piece, but never an "electron" shortage. So probably the latter is
journalistically s*xi*r. (* = e for the benefit of those with
prurience filters.) It does make me wonder what is in those science
textbooks we've been hearing about; I'll bet at least one of them says
that electricity is made out of electrons.

When I was reading about the direction of voltages, I wanted to hear about
electric field vectors applying forces to cause the drift of electrons.
Which comes first the field or the voltage?

I fear I am getting myself into trouble tonight!

The gravitational analog would be to ask which comes first, the
(non-general relativistic) vector gravitational field or the scalar
gravitational potential energy field associated with it. I'm pretty
sure that the existence of one implies that of the other (unless
you're willing to instigate another F=ma -like thread, which will, as
you fear, almost certainly get you into trouble with this NG!)

I'm curious that no one has suggested this model of a very low
frequency, non-sinusoidal AC circuit (my understanding is that AC
technically means the signal reverses periodically, but is not
necessarily sinusoidal), constructed from a switch, light bulb, and
battery in a series loop. Close the switch for ten seconds to light
the bulb. Then open it for ten seconds. While the switch is open,
reverse the leads on the battery. Close the switch for another ten
seconds, observing the reversal of current but continued positive
transduction of energy in the light bulb. Open the switch ... Positive
transduction during both "duty phases" should be easy to understand on
the basis of DC circuit theory alone.

Repeat ad nauseum and you have a step-function generator of
fundamental frequency 0.025 Hz. Take the Gedankenlimit (mangled German
for "don't try this at home") as the lead-reversal downtime approaches
zero and you approach a garden-variety square-wave generator of
frequency ~0.050 Hz. Speeding up the process to any reasonable
frequency (period >> signal propagation time) and filtering off the
corners of the square-wave to make it sinusoidal should not affect the
continuing positive energy transduction occurring within the light
bulb during either half of each cycle. Of course, at sufficiently high
frequencies, inductive and radiative effects would limit the current
and the bulb would dim, but it would still produce heat (if not light)
during each half-cycle.