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capacitor discharge time

Discussion in 'Misc Electronics' started by exxos, Jul 13, 2004.

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  1. exxos

    exxos Guest

    Hi all,

    If I have a 100uF capacitor charged to 12volts, then I place a 6R ressitor
    across is (2amps) how long would it take to discharge to say 10volts ? How
    do I work this out ?

  2. Bill Bowden

    Bill Bowden Guest

    Subtract the voltage change (2) from the starting voltage (12)
    and you get 10. Divide this by the starting voltage 10/12 and
    you get 0.833. Find natural log of this and you get -0.182
    Next, multiply by RC and you get -.182 *6 * 0.0001 = -.000109
    Change sign to positive and the answer is 109 microseconds.

    t = - log ((V-delta V)/V) * RC

    t = - log ((12-2)/12) * .0006 = 109 uS

  3. Mantra

    Mantra Guest

    Homework problem?

    V = Vo exp(-t/RC)
  4. exxos

    exxos Guest

    Everyone always says this ;), actually , I've been in the electronis repair
    trade for the past 15 years, unfortunatly working out stuff isn't by far in
    my day to day role, and since I have a memory like a siv one tends to forget
    over time :(
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