# Homework Help: RC Circuits HELP!

1. Sep 12, 2010

### sl02ggp

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

Find the voltage across a capacitor in an RC Circuit, using [V]_{}[/c] (0) = 1, [V]_{}[/i] n(t)=t.

2. Relevant equations
dV/dt = (1/RC)(V)=(1/RC)([V]_{}[/in])

3. The attempt at a solution
New to this site: I honestly don't know where to start. Done well in Calculus. Feel DifEq is like a breed of its own..aha

I know you have to use this type of an equation: VC = V0(1− e−t /τ ) where τ = RC and V0 is the initial voltage

2. Sep 12, 2010

### sl02ggp

anyone?

3. Sep 12, 2010

### psholtz

I'm a little confused by your equations..

In general the voltage across a series RC circuit will decay exponentially, on a time constant determined by the value of RC.

The voltage across a resistor is:

$$V_R = IR = R\frac{dQ}{dt}$$

The voltage across a capacitor is:

$$V_C = Q/C$$

Knowing this, you should be able to set up a simple differential equation which will provide the answer you desire.