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Homework Help: Show that Q is proportional to V for capacitor

  1. May 29, 2012 #1
    1. The problem statement, all variables and given/known data
    Describe how you would show experimentally that the charge stored on a 220 µF capacitor is proportional to the potential difference across the capacitor for a range of potential differences between 0 and 15 V. Your answer should include a circuit diagram.


    2. Relevant equations



    3. The attempt at a solution

    attachment.php?attachmentid=152384&d=1338318521.png

    - charge the capacitor for a given Voltage, V
    - ensure the capacitor is charging at a constant rate by varying the resistance of the variable resistor --> ensures current remains constant
    - Q=It (current * time take for capacitor to charge)
    - capacitor is charged when V on meter = V of supply
    - Q/V = constant for range of values of V

    Is this method correct - would it work?

    p.s: I am aware my diagram is not very well drawn - i will obviously improve this in the exam
     
  2. jcsd
  3. May 29, 2012 #2
    V is easy to measure....do you know of any way to measure Q?
     
  4. May 29, 2012 #3
    my syllabus only talks about coloumbmeters but the MS said the a coloumbeter would be insufficient for this experiment because the capacitance is too high.

    I was simply wondering, would my method work?
     
  5. May 30, 2012 #4
    Your method sounds good to me - although it might be a bit tricky keeping the current constant unless the capacitor was charging very slowly.
     
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