Capacitors connected in series?

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    Capacitors Series
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Discussion Overview

The discussion revolves around the behavior of capacitors when connected in series and then reconnected in various configurations, particularly focusing on charge distribution and potential differences. Participants explore theoretical implications, calculations, and practical considerations related to capacitor circuits.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant proposes that when two capacitors are connected in series and then disconnected from a battery, they will retain a charge of 2Q when reconnected in series.
  • Another participant counters that the charges in a circuit are a "zero-sum" entity, suggesting that reconnecting the capacitors without a battery would lead to equalization of charge, resulting in zero charge everywhere.
  • Some participants discuss the implications of reconnecting capacitors in parallel versus series, with one noting that in parallel, the total charge remains 2Q.
  • There is a suggestion that if capacitors are reconnected with their terminals crossed, a surplus charge could be observed on the wire segment, although this claim is contested by others.
  • Participants present equations relating charge (Q), capacitance (C), and voltage (V) to illustrate their points, with some emphasizing the role of resistance in the circuit during discharge.
  • One participant mentions that reconnecting the battery after crossing the terminals could lead to further charging of the capacitors, while others express skepticism about the sequence of events leading to discharge or charge accumulation.
  • Disagreements arise regarding the sequence of discharging and charging, with some participants questioning the validity of proposed diagrams and the assumptions behind them.
  • There is a discussion about the potential for infinite self-charging, with some participants asserting that this is impossible.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as multiple competing views remain regarding the behavior of capacitors when reconnected in different configurations. Disagreements persist about the implications of charge distribution and the effects of reconnecting to a battery.

Contextual Notes

Some participants express confusion over the sequence of operations and the resulting charge states of the capacitors, indicating that assumptions about charge and potential may not be clearly defined in the discussion.

  • #31
re post #23 (Bottom left corner of the diagram)

The bottom capacitor goes from +Q, -Q to 0Q, +2Q. So the voltage polarity has reversed. That certainly looks like it's been discharged and recharged in the opposite direction :-)

A change from -Q to +2Q implies a current of 3Q flowed. Yet other nodes change from +Q to +2Q which is only an increase of Q. How is that possible if they are in series?
 
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  • #32
rumborak said:
Sorry, had not noticed the reversal of charges in case 3. But still, case 1 you can't really calculate like that. The formulas you are using presume ideal components; at the moment of your case 1 picture, you are short-circuiting ideal components. Meaning you have infinite current, and an unaccounted-for potential difference between the capacitors.
mmm, but i think all that in the paper doesn't hold unless c1 = c2, the final answers wouldn't change but the steps would change, for example in case 2 if c1 not equal c2 therefore Q1 will not be equal to Q2 but there summation still will be 2Q
 
  • #33
@CWatters, crap, you are correct, the picture is incorrect. The two right plates should read -2Q (top) and 0Q (bottom). Which would mean, when you cross them over, you are connecting a 2Q to -2Q. The reversal of polarity is what kills it in the end.

It was a nice idea, lol.

EDIT: Thinking about it more, there's also the argument that charges are a zero-sum game. If I create a 2Q somewhere, somewhere else must be -2Q. The only way of reconnecting it without massive discharge would be to find another 2Q potential. Which really could only come from another device.
Hmmmmm, got to think more about this.
 
Last edited:
  • #34
so i think case one would only be short circuit when c1=c2 :D , but if c1 not equal c2 so voltage will be distributed not equally between them (because in series) so i think it will not be shorted
 
  • #35
Throw a few diodes into the mix and you can make a high voltage charge pump..

http://en.wikipedia.org/wiki/Cockcroft–Walton_generator

220px-Cockcroft_Walton_voltage_multiplier_circuit.svg.png
 

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