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Homework Help: Design a Capacitor

  1. Feb 15, 2009 #1
    1. The problem statement, all variables and given/known data
    You are to design a capacitor capable of providing the energy required to start a small motor. In particular, the capacitor must meet the following three requirements
    a) The capacitor must provide an average power of 10W for a time interval of 0.50 seconds
    b/ Macimum allowable Capacitor potential difference = 12V

    2. Relevant equations
    C = Q/V

    3. The attempt at a solution
    I am kinda stumped on the average power 10W over 0.5 seconds. Does that mean that i convert back into Energy of 5J or something else?
  2. jcsd
  3. Feb 15, 2009 #2
    You're missing a relevant equation. Look for one that defines energy in terms of capacitance and voltage.
  4. Feb 15, 2009 #3

    u = (1/2)cv² ?
  5. Feb 15, 2009 #4
    That's it.
  6. Feb 17, 2009 #5
    is there an equation or an explanation that will help me understand the values if the plates are a foil and rolled together, so it keeps the area needed at a reasonable size?
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