[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Household NEUTRAL is not really a return path



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:12 AM 9/17/2005, Tesla list wrote:
Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

As far as I know resistance and impedance are the same.
Not exactly.
Resistance is the real part of impedance. Reactance is the imaginary part.
You could have a "ground connection" that has zero ohms resistance, yet have a 1000 ohm impedance (i.e. an inductor of some sort), and that's why the distinction is important.

I prefer to avoid the abstraction of "imaginary" resistance, that is not a real thing, but just a mathematical trick to do the calculations, meaning that, if the voltage is a sinusoid, the current is a cosinusoid, at +/- 90 degrees with the voltage. Even so, this works only for sinusoidal signals (and periodical signals, if you decompose them in Fourier series).

Very true. I should have said that this works for "steady state" systems where decomposition into sinusoids is possible.




A resistor has always the same impedance, for any frequency.
A capacitor has an impedance proportional to the inverse of
the frequency, so it blocks DC and allows the passage of currents
that vary at high frequency.
An inductor has an impedance that is proportional to the
frequency, so it is a short-circuit at DC and blocks vast-varying
currents.

This gets to the differential equation approach, which for tesla coils (being hardly steady state devices) is probably a better model.


Mostly a time domain vs frequency domain question, and one of choosing an appropriate computation model for the questions you need answered.