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13h
comment what could generate a high-pitched whine in electronics where the frequency depends on the current?
@user6972, I concur about power supply switching frequencies in general; it all depends on the supply. However, high voltage supplies tend to run at lower frequencies because of the high effective capacitances presented by the high voltage transformer. Moreover: 1) I claim magnetostriction as part of the power supply, since the transformer is an element in it. 2) a steady sound usually requires a driving signal at the same or a related frequency, so just saying "magnetostriction" without identifying an underlying frequency source is not an answer, imho.
13h
comment Physical explanation for capacitive circuit
@IncnisMrsi, I take your point that my answer could be elaborated. Would you care to add an answer that does so?
15h
awarded  Revival
18h
comment How does current flow from the emitter, through the base and to the collector in a NPN transistor?
@IncnisMrsi, updated per your recommendation. Thanks!
18h
revised How does current flow from the emitter, through the base and to the collector in a NPN transistor?
specified "current gain" per comment.
1d
comment Reading the Feynman lectures in 2012
The potential-based approach to EM you mention may be "Collective Electrodynamics" by Feynman's student Carver Mead: en.wikipedia.org/wiki/Carver_Mead . PS: I recall you writing favorably of Steven Frautschi's S-Matrix book. I saw him recently; in retirement, now 80, he has re-invented himself as a teaching assistant, and won Caltech's Feynman Prize for Excellence in Teaching this year. When I mentioned his S-Matrix work being cited here, he ducked his head and said, "Well, that was a long time ago..."
1d
comment Reverse bias P-N junction
@IncnisMrsi, 1) Thanks, my wording was poor; I've attempted to improve it. (I meant excess in comparison with the unbiased junction.) 2) I concur. Apparently this ideal diode characteristic works fairly well in germanium diodes (because $I_0$ is larger than for silicon?), but in Si, other mechanisms, like carrier generation in the transition region, cause the reverse-bias current to vary with voltage.
1d
revised Reverse bias P-N junction
clarified wording
2d
comment Homemade salad dressing separates into layers after it sits for a while. Why doesn't this violate the 2nd law of thermodynamics?
After way too much time, I see that my criticism was incorrect. Apologies for my confusion...
2d
revised Homemade salad dressing separates into layers after it sits for a while. Why doesn't this violate the 2nd law of thermodynamics?
Correct error.
2d
comment Reverse bias P-N junction
@IncnisMrsi, I've added a sketch of stored-charge analysis, plus a link to reference with figures (which are always helpful).
2d
revised Reverse bias P-N junction
added stored-charge analysis sketch.
2d
comment Reverse bias P-N junction
@IncnisMrsi, yes, the depletion region is formed by depleted majority carriers. However, if you want to understand how much current flows in a reverse-biased diode (the question I'm addressing) you must focus on the minority carriers (the ones the applied field can sweep across the junction), and minority carrier concentrations are in fact depleted by a reverse bias. It's not an exclusive-or situation.
Oct
18
reviewed Approve suggested edit on Why do people recommend wider tyres in car for better road grip?
Oct
17
reviewed Approve suggested edit on How is antimatter made?
Oct
17
awarded  Civic Duty
Oct
17
answered Which BICEP2 r value should be compared to Planck's r<0.11?
Oct
17
answered Field of moving charge / Lorentz;Lienard-Wiechert
Oct
17
revised Feynman's proof for Liénard-Wiechert's potential of a moving charge
added analysis.
Oct
15
answered Feynman's proof for Liénard-Wiechert's potential of a moving charge