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Series vs. parallel capacitors

  1. Feb 25, 2010 #1
    1. The problem statement, all variables and given/known data

    I have some results of my lab here and I just want to check to make sure they make sense. The lab write-up refers to this part of the experiment as "capacitors in parallel" but I think they are actually in series (either that or we connected them incorrectly).

    Here is a portion of the lab write-up:

    For the formal experiment, begin with a pair of capacitors in parallel. Place a .1uF (the "u" should read as micro) mounted across the input of the voltage follower and mount a 1.0uF capacitor on a styrofoam block; connect the 2 capacitors to create a 1.1uF capacitor. Make sure that the 1.1uF is completely discharged. Charge a second 1.0uF capacitor to 5.0V and touch it to the uncharged 1.1uF capacitor. For safety, discharge the "charge-transfer" capacitor before putting it down. Compare the measured voltage to what is expected from a theoretical calculation.

    Our DVM (which was attached to the voltage follower) read 2.485V.

    I am confused because this part is labeled capacitors in parallel but it seems to me that when we touched the charged capacitor to the 1.1uF capacitor we made a series circuit, and that is why the voltage was not constant.

    Does this seem right to anyone?


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 25, 2010 #2

    Delphi51

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    Homework Helper

    It says to connect the 1 and the .1 to make a 1.1 microfarad capacitance, so you should have connected them in parallel. That is, connect them together at one end and also at the other end.

    However, in this case when you touch the 1 μf capacitor (1 nearly equal to 1.1) you ought to get about half of the 5 Volts on each rather than 2.485 V.
    Perhaps you can work out what the capacitance and voltage are if they are in series and see if that works out to about the 2.4 V.
     
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