Capacitance in a series circuit

Discussion in 'Homework Help' started by kevin monroe, Nov 14, 2014.

  1. kevin monroe

    Thread Starter New Member

    Nov 7, 2014
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    My electronics book says "Because the current throughout a series circuit is the same at any point, capacitors connected in series have the same number of coulombs (C) of charge (Q)."
    Is this statement true without qualification? It seems like only capacitors of equal capacitance would have equal charge. Wouldn't the charge vary with the capacitance of the capacitor?
    Thanks for any help.
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    It is true,they will all store equal charge even when capacitance is different.
     
  3. kevin monroe

    Thread Starter New Member

    Nov 7, 2014
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    Thanks! That's weird.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    Not really. Since Q = CV the voltage across different size capacitors in series will be different so they each has the same charge . For example if you apply 3V to a 1uF cap in series with a 2uF cap than the 1uf will end up with 2V across it and the 2uF will have 1V across it, giving the same charge transferred to each capacitor.
     
  5. ISB123

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  6. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    If you want weird, try mechanical engineering.
     
  7. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Or, similarly, astrology.
     
  8. Papabravo

    Expert

    Feb 24, 2006
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    Financial Engineering and the Stochastic Calculus gets my vote for weird.
     
  9. kevin monroe

    Thread Starter New Member

    Nov 7, 2014
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    Thanks a lot!
     
  10. kevin monroe

    Thread Starter New Member

    Nov 7, 2014
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    Thanks for the 1 hour effort!!
     
  11. WBahn

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    Mar 31, 2012
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    It's not true without qualification, because it is possible for the capacitors to start out with different amounts of charge on them and this difference will be preserved. Also, for real capacitors (particularly larger value and certain types of electrolytics) there will be a leakage current that will tend to discharge the caps at different rates. For this reason, putting capacitors in series in real circuits is generally discouraged. But on paper what your books says is correct in principle.
     
  12. kevin monroe

    Thread Starter New Member

    Nov 7, 2014
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    thx
     
  13. ISB123

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    May 21, 2014
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    Capacitors in series will withstand more voltage.
     
  14. WBahn

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    Mar 31, 2012
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    And if you rely on this, sooner or later you will be in for a big surprise as, due to leakage mismatch, one of the caps will take on way more voltage than it is rated for.
     
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