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  1. H

    Permanent magnets and "permeance"

    I have an indoor recumbent exerciser bike that uses a non-contact magnetic "clutch" for resistance. There is permanent-magnetic fulcrum assembly that pivots on a hinge. And a heavy iron flywheel that spins when pedaling. The arc moves toward/away from flywheel based on resistance setting...
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    Harmonics in the "electrical" domain

    There is some controversy as to why the spectral content of vinyl records contain frequency "information" above what the analog tape recorder was capable of capturing. A thought experiment: If I have a piano that has a key which plays 15khz (primary freq. of that key's piano string), what...
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    Thermal ballast (or whatever it's called!)

    During weather-based heat waves or cold snaps, a completely sealed house with all windows/doors shut (but using no HVAC, heating-ventilation-AC) will take "a while" to cool down or heat up. If the heat wave or cold snap is quick (e.g., 24 hrs), a resident inside the house will experience almost...
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    Image frequencies

    In digital electronics -- and notably digital reconstruction filters, Shannon and Nyquist theorems -- one encounters "images" (or frequency images). In digital audio, for example, after the DAC (digital-to-analog converter), one must filter the output of the DAC with an anti-imaging filter...
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    B Is a single (naked) proton atomic/elemental Hydrogen

    Okay ... some "simple" questions (I think): If a single baryonic proton magically appears in a pure vacuum container (which is otherwise completely empty), can that proton be considered a positive Hydrogen ion? Or must a Hydrogen atom lose an electron first (so we just end up with a single...
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    B Mass of Sun/stars (elemental/molecular vs. plasma)

    I'm confused about the mass of the Sun (and stars in general). Wikipedia notes: " It is a nearly perfect sphere of hot plasma..." ...and later ... "About three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), ..." I...