Capacitor charging

Discussion in 'General Electronics Chat' started by Sparky49, Nov 30, 2012.

  1. Sparky49

    Thread Starter Active Member

    Jul 16, 2011
    834
    417
    Hi all.

    I know we can use the V(t)=Vi(1-e^(-t/RC)) equation to get the discharge time for a capacitor, but I am stuck when it comes to another formula.

    I need to figure out the time to get to 10Volts, when 1mA current charges a 1uF capacitor.

    I know that I=C(dV/dt), and have rearranged to get V(t)=(I/C)t, however I am not sure where to go from here.

    Many thanks.

    Sparky
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    Actually, no. You have the wrong equation and the right equation.
    The equation for discharge is V(t)=Vi(e^(-t/RC)).
    What you have shown is the equation for charging.
     
  3. bretm

    Member

    Feb 6, 2012
    152
    24
    You have V(t)=(I/C)t. You know V(t)=10V, you know I=1mA, you know C=1uF, you just need to know t.

    10V = (1mA / 1uF) t = (1000 V/s) t

    So t=10ms
     
    #12 likes this.
  4. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    I am sorry I misread the question. bretm is correct. Since the charging current is constant, V(t) increases linearly with t.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Since this is more of an electronics problem, I am moving this to the electronics chat form.
     
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