RE: Capacitor - series?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luke" <Bluu-at-cox-dot-net> 

Ok all this has me a bit confused.
I am STILL of the inclination that:
the two caps WILL NOT see the same voltage
if they are of DIFFERENT VALUES.

Some are saying they will see the same voltage.

What seems to be the verdict among the guys that know their stuff?

Luke Galyan
Bluu-at-cox-dot-net

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, February 08, 2004 3:06 PM
To: tesla-at-pupman-dot-com
Subject: Re: Capacitor - series?

Original poster: Mddeming-at-aol-dot-com


Hi Phil,  (see interspersed comments)

     In a message dated 2/8/04 2:25:06 PM Eastern Standard Time,
tesla-at-pupman-dot-com writes:

SNIPPPP

  >Firstly, at ac, just pick a frequency, calculate Xc, treat them as two
  >(or 5) resistors & see what you get.  Better still wire it up & get
out
  >your meter - this you can measure.

Yeah! Scientific method!  Unfortunately, far too many people are willing
to
jump right to opinion without this step.

  >The voltage will divide across capacitors in inverse proportion to
their
  >capacitance - i.e. in direct proportion to their reactances, just as
if
  >they were resistors.
Correct.
  >It is the same for DC, can be explained by conservation of charge, but
  >is harder to measure.  Well not really, just use a DMM & uF range
caps.
  >[Time constant = (10M Ohm x 10uF) = 100sec - long enough to measure]

  >Because the circuit does not see the full
  >capacitance of any single capacitor in series, you can't use that
  >individual cap value to figure reactance because that caps true value
is
  >never "felt" by the circuit.  See my other reply.

  >It matters less in this discussion what the circuit sees than what the
  >individual capacitors see. In any case whichever way you do the maths
  >you get the same result.

  >The two capacitors -are- two discrete components. The electrons flow
out
  >of one & into the other. It makes sense to discuss their parameters
  >individually, which was the point of the original question.

Yes!!

  >If the original question's basic intent is something like: "Will one
or
  >both capacitors blow up when used in a TC tank circuit ?" then my
answer
  >would be along the lines of 'Not necessarily with those two examples
  >(equal C.V products), but often yes.'

  >Sure the smaller cap governs the charging characteristics & limits the
  >maximum charge of the combination - when it's charged the current
stops
  >flowing & they both stop charging. So it is more nearly fully charged,
  >and the larger cap less fully charged (To its capacity, I mean. The
  >absolute Charge contained in each cap is the same.)
Yes!!

  >In any given instant or cycle or whatever, the same current has flowed
  >through each capacitor. So they each hold an identical charge - no of
  >electrons. But a given amount of charge, if you like, concentrated in
a
  >smaller volume (capacitance) results in a higher pressure (voltage) &
  >vice-versa.

  >Q = C.V  ->  V = Q/C    That pretty much says it.


  >Phil Chalk.

   Of course, you are right. You obviously have a sound understanding of
first principles, but it is amazing how much mis-information one can
find,
even on this list. What frightens me is the number of Newbies and
Not-so-newbie "self-ordained experts" who are actively working with high

voltages and advising others, with only a minimal (or less)
understanding
of basic principles of electricity. This capacitor question is only one
small example of the larger problem.

There was a time when cost of publication and peer review acted as B.S.
filters, but now anyone with an opinion and the price of a keyboard can
"fertilize" the whole Internet in a matter of minutes. While I am in no
way
in favor of censorship of the list, it would be nice, (but practically
impossible) if statements that are blatantly contrary to all known
physical
laws could be annotated as such before being rebroadcast. Oh well, I
guess
our after-the-fact reviews are the best that can be done. I just hope
that
newbies can figure out who is "blowing smoke" before they blow their
coils,
their instruments, or themselves up in smoke.

Matt D.