Re: Loading Coils; was : Vincent antenna

Earlier, I wrote:
AI4QJ wrote:
In an inductor, current lags voltage. If you connect a resitor and a coil in parallel and apply AC, EE101 tells you that, although the phase of the voltage across them stays the same, the current is "delayed" by the phase angle in the inductor when compared to current resistor.

No, it isn't - the phase of the current around the circuit has to stay the same. Think of the simplest possible circuit: an AC voltage source (of zero internal impedance) with one terminal wired to R, lumped L in series, and directly back to the other terminal of the AC source. If the phase of the current were delayed through L as you suggest, there would then be a difference in phase between the two terminals of the AC source... which is obviously not true.

It's the magnitude and phase of the voltage that varies at different points around the circuit; but the magnitude and phase of the current has to remain the same all the way around the loop. In more formal terms, Kirchhoff's current law applies all around the circuit; and it most certainly applies between the two terminals of a lumped inductance.

My apologies to AI4QJ. He was talking about a parallel R-L circuit, and my reply was about a series R-L circuit. Each of our statements was correct in its own context.

Thanks to Tom B for pointing this out.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
.

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