How do I calculate the time it takes to discharge a capacitor?

[puhdanks]

I have a test coming up and i know what some question will be on. One question is about the time it takes to discharge a capacitor from "full" to a given point or percent of initial charge. How would i go about doing this.



I know the it has to do with the time constant RC and the equation of discharging a capacitor i just don't know how i would find the time it takes.

The Attempt at a Solution

 

[phinds]

You said you know the equation for discharging a capacitor, so what is that equation? Is it not an equation for the TIME to discharge a capacitor? If not, what is it?

 

[puhdanks]

well i guess i should have said i think i need to use it and its [q=q(naught)e^(-t/RC)]

 

[puhdanks]

does it just become [(percent droped)=e^(t/rc) i will probably be given r and c

 

[phinds]

Yes, you have right idea, so now how do you solve that for t ?