Capacitor charging

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

1. Sparky49 Thread Starter Well-Known Member

Jul 16, 2011
835
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
12,648
3,458
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
12,648
3,458
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
20,772
2,540
Since this is more of an electronics problem, I am moving this to the electronics chat form.