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Calculate capacitance to adjust current in ac circuit

  1. Mar 21, 2010 #1
    1. The problem statement, all variables and given/known data

    A Purely resistive resistive 100w, 110v lamp is to be supplied by an a.c. source of 230v r.m.s at 50Hz. what value of pure capacitance could be put in series to adjust the current flow to a suitable value?

    2. Relevant equations
    p=iv
    q=cv
    v=ir
    i know a number of other time dependant equations but i dont want to list them all pointlessly

    3. The attempt at a solution
    Im not sure of how best to approach this, i dont have much experience with AC circuits. i know the current at the lamp is 0.909 amps, from p =iv. but id appreciate a push in the right direction

    cheers,khris
     
  2. jcsd
  3. Mar 21, 2010 #2
    If you were to add a resistor to limit the current instead of a capacitor, could you calculate how much total resistance is needed to limit the current to the correct value?

    Do you know how are reactances and resistances added?

    Can you do that process in reverse separating the total impedance needed (calculated in the first step) into resistance and capacitive reactance.

    Can you calculate capacitance from capacitive reactance and frequency?
     
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