# Homework Help: I need some help on RC circuit

1. Mar 22, 2013

### physics=world

1. The problem statement, all variables and given/known data

I'm trying to use the equation for charging capacitor that's discharging, and I can't get the answer right. On the calculator it keeps showing as 1.

2. Relevant equations

I(t) = -(1.96) [e^((-9.0*10^(-6)) / (1300)(2.0*10^(-9)))]

3. The attempt at a solution

My problem is that the exponential part keeps coming out as the value 1 when I input it into the calculator. I need help on solving the exponential part.

Last edited by a moderator: Mar 22, 2013
2. Mar 22, 2013

### voko

Is the equation $$-1.96 \exp{\frac {-9.0*10^{-6}}{1300*2.0*10^{-9}}}$$ or is it $$-1.96 \exp({\frac {-9.0*10^{-6}}{1300}2.0*10^{-9}})$$?

3. Mar 22, 2013

### physics=world

the first one... e^(-t/RC)

4. Mar 22, 2013

### voko

The way you typed it, however, it will be interpreted as #2. You need additional brackets to enforce #1, OR you must use the division operation twice.

5. Mar 22, 2013

### physics=world

oh. thank you for the clarity. it works.:rofl: