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In Reply to: RE: It's there in black and white. posted by Mark Kelly on August 25, 2014 at 00:41:20
"Short version: he's using an analogy to estimate the ratio of field strength to applied voltage."
Yes, provided that by "field strength" you mean the displacement field, D, and not the electric field E. The current flowing through the capacitor is proportional to dD/dt rather than dE/dt, and that's why he gets a D vs. E curve.
I'm not sure why you say "analogy." Seems like the real thing here?
Chris
Follow Ups:
It's an analogy because he's not measuring D directly, he's measuring an analogue of it.
Mark Kelly
"It's an analogy because he's not measuring D directly, he's measuring an analogue of it."Hmmm...I suppose it comes down to semantics, really. By the same token, one could say that he's not measuring the current directly, but an analogue of it, since he is actually measuring the voltage drop across a resistor, and then using Ohm's law.
In one case Ohm's law is used, in the other case, a Maxwell equation.
If one starts on that path, then in the end all of life and existence is just an analogy, with the only "measurements" being our conscious perceptions in the mind...
Chris
Edits: 08/25/14
"If one starts on that path, then in the end all of life and existence is just an analogy"
You're lucky Ayn Rand is no longer with us. :)
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