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Capacitance and voltage relationship

  1. Jun 5, 2012 #1
    1. The problem statement, all variables and given/known data

    The actual value of the capacitor Rahal will receive may be different from the value the
    catalogue states. The manufacturer guarantees that the maximum percentage difference
    below/above the catalogue value will be –10% / +50%. Rahal orders one of the 400 V 1000 µF capacitors. Within what range will its actual value lie?

    2. Relevant equations

    Q=CV
    therefore C is inversely proportional to V
    3. The attempt at a solution

    I would say:
    1100µF = max
    500µF = min

    BUT THE ANSWER IS
    900µF = min
    1500µF = max

    WHY???

    thanks
     
    Last edited: Jun 5, 2012
  2. jcsd
  3. Jun 5, 2012 #2
    The stated capacitance is 1000.

    The possible variance is -10% to +50%.

    What is 10% of 1000 subtracted from 1000?
    What is 50% of 1000 added to one thousand?
     
  4. Jun 5, 2012 #3
    but the variance is for the voltage...
     
  5. Jun 5, 2012 #4
    Where is that stated?
    If so, why is the answer given farads?

    Additionally, bearing in mind that I'm yet to study capacitors in any level of detail, does the voltage not correspond to a maximum input voltage that the device can handle without being damaged, destroyed, or at least cease to function?
     
  6. Jun 5, 2012 #5
    The manufacturer guarantees that the maximum percentage difference
    below/above the catalogue value will be –10% / +50%.
     
  7. Jun 5, 2012 #6
    Are you reading "percentage difference" as "percentage potential difference" or something similar?
     
  8. Jun 5, 2012 #7
    yes...oops
    thanks
     
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