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RE: Units of electricity

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 05:19 PM 8/24/2006, Tesla list wrote:
Original poster: "Godfrey Loudner" <ggreen@xxxxxxxx>

I think these matters are sufficiently explained in "Advanced
Engineering Mathematics, Wylie, McGraw-Hill, Fourth Edition. See Chapter
5, Mechanical Circuits and Electrical Circuits. While its nice to know
about the analogy, I never found it useful in my electricity hobby. In
the practical sense, it might be useful and cheaper to build an electric
circuit analog of a mechanical system to predict performance;

And such was done.. Analog computers were heavily used to do just this, probably up into the 60s, when digital computers got fast enough. There's all kinds of nifty modules available to do things like backlash, nonlinearities, saturation, etc. Look for stuff from Burr-Brown or Philbrick. many, many control systems were designed with analog computer testing.

 but I
don't think the analogy has any great theoretical value.

Not so much the analogy, but the fact that you can move back and forth with a consistent set of units is what makes things like motor design, and loudspeaker design, even doable in an analytical sense. Electromechanical devices, in general, are transformers from one medium to another. Run a loudspeaker in a helium atmosphere, and the terminal impedance will be different, because the inertial loads from the atmosphere when it moves are different.