# RC Circuit Problem

1. Oct 3, 2004

### gregbellows

Hi,

I am stuck on a question to work out the value of a capacitor,

The Question is:
A capacitor and a 2Kohm resistor pass the same current when each is separately connected across a 100Hz power line.
What is the value of the capacitor?

2. Oct 3, 2004

### chroot

Staff Emeritus
The impedance of a capacitor is

$$\frac{1}{j \omega C}$$.

The resistance of the capacitor at 100 Hz is just the real part of that impedance (this is the hard part). Use Ohm's law (V = ZI) to solve for the capacitance.

- Warren

- Warren

3. Oct 3, 2004

### don rigby

ohms law shows us that e = i times r, when considering capacitance and frequencies, we substitute r with Xc (capacitive reactance). when a frequency is applied to a capacitor it allows current flow at a rate of ;
Xc=1/[2 * pie(3.14) * f (freq.) *c(farrads)]
***this is the formula for the impedence of a capacitor.
Xc= 2000, f= 100:
therfore C= ???? you do the math

Last edited: Oct 3, 2004