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Homework Help: Solving capacitor circuits? Help?

  1. Jan 31, 2012 #1
    Not sure If I posted this is the correct place -Im new
    hi, I am working on a college assignment. I'm on a day release program and unfortunately I missed the day where we covered this part. Please could someone help me?

    The questions I need to answer are:

    a) For each capacitor shown in figure 12 determine the charge, energy stored and voltage across EACH capacitor.

    Figure 12 is:

    200V DC series circuit with 3 capacitors C1 = 4 μF C2= 8 μF C3 = 10 μF

    b) (same question different diagram)

    Figure 13 is:

    100v rail with two capacitors in parallel.
    C1 = 12 μF
    C2 = 2 μF

    If someone could help me out here I would be very great full, When I say help me out, I dont mean tell me the answers, more tell me how to find the answers.


  2. jcsd
  3. Jan 31, 2012 #2
    If you have 4μF, 8μF and 10μF in series do you know how to calculate the combined capacitance? (I got 0.475μF)
    Can you then calculate the charge in the combination.... this is tricky... charge on capacitors in series is a bit tricky.... depeneds on the level you are up to
    Hope this gets you going
  4. Jan 31, 2012 #3
    I know some stuff, I can sort of do parallel from some handouts I was given the week after. However, When it comes to series I run straight into a wall.
  5. Jan 31, 2012 #4
    sorry Grandsatsuma..... something went wrong in my post.... I got combined C = 2.1μF
    NOT 0.475.... posted before I had finished somehow !!!
  6. Jan 31, 2012 #5
    can you see how I got 2.1μF?
  7. Jan 31, 2012 #6
    I think I can, I did product over sum and got 2.1052
  8. Jan 31, 2012 #7
    For capacitors in series the combined capacitance is given by 1/C = 1/C1 + 1/C2 + 1/C3....
    Check that it gives 2.1μF....
    The voltage is 200V so can you calculate the charge on the combined capacitance?...this s easy.
    Now can you calculate the charge on each capacitance . There is a formula for this but. You may find it tricky to sort out......this s one of the trickiest things to understand about capacitors.
    Ibwill get back to you.
  9. Feb 1, 2012 #8
    I managed to workout that the overall charge is 420.8 and the combined capacitance is 2.104

    How would I work out the individual charge, voltage across and energy stored for each capacitor?
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