# Homework Help: Capacitor in an AC circuit

1. Apr 7, 2016

### ReidMerrill

1. The problem statement, all variables and given/known data
A capacitor has a peak current of 240 μA when the peak voltage at 250 kHz is 2.7 V .
Part A
What is the capacitance?

Part B
If the peak voltage is held constant, what is the peak current at 500 kHz

2. Relevant equations
Xc=1/wC
Vc=IcXc

3. The attempt at a solution
I rearranged equation 2 to solve for Xc = 2.7V/0.000240A = 11250
I then rearranged equation to to solve for C =1/wXc = 3.56x10-4

This is not correct. Why is this not correct and what is the proper way to go about solving it?
Thank you.

Correction: I re-did the second calculation and got 3.56x10-10F by properly converting kHz to Hz but it's still wrong.

Last edited: Apr 7, 2016
2. Apr 7, 2016

### Staff: Mentor

Hi ReidMerrill.

Did you convert kHz to radians/sec?

3. Apr 7, 2016

### ReidMerrill

Oh you know what I did not. I wasn't aware I needed to. My professor did not explain this well at all.
I would just divide the frequency by 2pi, correct?

EDIT: That worked. Thank you!