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

 

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.

 

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

 

I am sorry I misread the question. bretm is correct. Since the charging current is constant, V(t) increases linearly with t.

 

Since this is more of an electronics problem, I am moving this to the electronics chat form.