[sdiy] L, C, and sometimes R

[jhno]

i really like how this page explains the basics of inductors and capacitors:

http://www.nzart.org.nz/nzart/examinat/amateur%20radio%20study%20guide/Course%20Files/Caps%20Inductors%20Resonance/STUDY%20NOTES%20-%20CAPACITORS%20INDUCTORS%20&%20RESONANCE.htm

much clearer (to me) than everything else i have read.

interestingly, it talks about e.g. capacitive and inductive reactances
combining to make a notch filter, by causing very little current to flow at
the resonant frequency.

hmmm. i usually think of it like this:


- capacitors (C) pass high frequencies; inductors (L) pass low frequencies.
therefore, a series C is an HPF, and a series L is an LPF.

- in parallel connection, those frequencies are shunted to ground instead
of passed on. hence a parallel C is an LPF, and a parallel L is an HPF.


so how incomplete or inaccurate is this over-simplified model? in what
practical aspect does it fail, when designing/analyzing high-quality audio
circuits?


i think the main problem is that i tend to think of circuits operating as a
state machine of voltages. it seems like if you know all R and V in a
circuit, you have all the information - since I can be derived from them.
hence I seems like extraneous information and really just a different way
of looking at the system. it is useful to use this point of view when
calculating the behaviour of a transistor or tube, but couldn't all that
information technically be represented, albeit awkwardly, in terms of R and
V?

in any case, my lack of intuition for I and V mean that i do not easily
understand e.g. the effects of the opposite phase shifts imposed by L and
C, and the relationship or combination of capacitive and inductive
reactance.

please reveal the crucial point that makes it all fall into place - !

jhno