Layra-chan
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- Posted: Tue, 29 Oct 2013 06:47:47 +0000
chainmailleman
Layra-chan
Just to be clear, I don't mean "observable" as in "what people see". That's not a very meaningful idea in physics. I mean observable in the more technical sense of "this is what can be calculated from experimental data."
Also, yes, there are waves that exhibit behaviors that exceed the speed of light. In particular, the group velocity of a wave can exceed c, but that's okay; the c limit is on the phase velocity, not the group velocity. If you can exhibit a wave in which the individual peaks and troughs of the wave are moving faster than c, that's a very different story, but simply getting the shape of a pulse to move faster than c is not violating relativity at all.
Also, yes, there are waves that exhibit behaviors that exceed the speed of light. In particular, the group velocity of a wave can exceed c, but that's okay; the c limit is on the phase velocity, not the group velocity. If you can exhibit a wave in which the individual peaks and troughs of the wave are moving faster than c, that's a very different story, but simply getting the shape of a pulse to move faster than c is not violating relativity at all.
C is the limit of phase velocity of 90 degrees. Voltage and current exist at right angles to eachother.
When both voltage and current exist in phase and in a single vector, C is not the limit. Pi/2*C becomes the limit.
Again, current and voltage are group velocity phenomena so the limit of c isn't expected to hold for them anyway. I'm not sure if we're actually contradicting each other here, although I would like to see a derivation of the limit of Pi/2*C for voltage and current being in phase. As far as I know, there isn't actually any limit on group velocity.
And I kind of screwed up; it's not phase velocity either. Both group velocity and phase velocity can exceed the speed of light using various anomalous dispersion techniques; it's signal velocity that is bounded.