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

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To calculate the time it takes to discharge a capacitor, the key equation is q = q₀e^(-t/RC), where q is the charge at time t, q₀ is the initial charge, R is resistance, and C is capacitance. To find the time t for a specific percentage drop in charge, rearrange the equation to isolate t. This involves taking the natural logarithm of both sides and solving for t, resulting in t = -RC * ln(q/q₀). Knowing the values of R and C will allow for the calculation of discharge time. Understanding this process is essential for preparing for the test question.
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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

 
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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?
 
well i guess i should have said i think i need to use it and its [q=q(naught)e^(-t/RC)]
 
does it just become [(percent droped)=e^(t/rc) i will probably be given r and c
 
Yes, you have right idea, so now how do you solve that for t ?
 

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