# Capacitor charging solved for time.

1. Jan 22, 2013

### MidlandSoul

1. The problem statement, all variables and given/known data
Solving the equation: V = V0*[1 - e^(-t/RC)]

2. Relevant equations
Need to solve this equation for time to calculate the time at which a charging capacitor achieves a certain voltage across it's plates.

3. The attempt at a solution
I solve it as: t = -RC*ln(V/V0) but this doesn't seem to work. Help!

2. Jan 22, 2013

### BruceW

it looks like you might have done a step like this: ln(1+x) = ln(x) But this is not true.

Edit: Oh, welcome to physicsforums by the way!

3. Jan 22, 2013

### rude man

Show your work step by step & we'll show you where you went wrong.

4. Jan 22, 2013

### haruspex

Or rather, ln(1-x) = ln(x)

5. Jan 23, 2013

### MidlandSoul

Thanks guys. I think our lecturer intends for us to sort of 'have a guess' by inspection and using time constant ratios than actually solve this, so I can leave it for another day, phew!
Thank you for the feedback nonetheless.