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Homework Help: A couple circuit problems

  1. Jan 30, 2005 #1
    1. For http://www.pen.eiu.edu/~cuemc4/circuit.bmp [Broken] picture.. Calculate the potential at point D.

    2. I 15-V battery is connected to three capacitors in series. The capacitors have the following capacitances: 4.5microFarads, 12.0microFarads, and 32microFarads. Find the voltage across the 32microFarad capacitor.

    I am so lost. :frown:
     
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Jan 30, 2005 #2
    Please? I'm desperate!
     
  4. Jan 31, 2005 #3

    learningphysics

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    I couldn't open your first picture... I get a "server not found" message.

    For the second one... first find the equivalent total capacitance (combine 3 capacitors in series). The find the total charge on this equivalent capacitor.

    You should then be able to get the charge on each capacitor (hint: this is really simple... if you are unsure read your textbook regarding combining series and parallel capacitors), and then get the voltage on each capacitor.
     
  5. Jan 31, 2005 #4
    http://www.pen.eiu.edu/~cuemc4/circuit.bmp [Broken]

    That might work. Mak sure you're soomed in all the way or it wont look right. Thanks for the help so far!
     
    Last edited by a moderator: May 1, 2017
  6. Jan 31, 2005 #5

    learningphysics

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    New link doesn't work either.
     
  7. Jan 31, 2005 #6
    I'll attatch it.
     

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  8. Jan 31, 2005 #7

    learningphysics

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    Hmmm... absolute potential can't be calculated unless there's ground assigned somewhere. But I don't see one on the circuit. Are you sure the question asks for potential at D and not potential difference between 2 different points? Does the question mention about 0 volts being assigned somehwere?
     
  9. Jan 31, 2005 #8
    Sorry. It says point A is grounded (V=0).
     
  10. Jan 31, 2005 #9

    learningphysics

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    ok cool. So first find the current I in the circuit using KVL. So then you can get all the voltage drops across all the resistors (voltage drop across a resistor=current*resistance). Using that you should be able to find the potential at D. Be careful with signs!!

    Hope this helps!
     
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