# Help with R C and frequency

Discussion in 'Homework Help' started by tegman, Apr 30, 2009.

1. ### tegman Thread Starter New Member

Apr 30, 2009
3
0
Im having a problem with a ? in my book.

A 47Ω load resistor is connected in series with a 10 microfared capacitor. At what freq. will the capacitor reach the same value as the load resistor?

Aron

2. ### PRS Well-Known Member

Aug 24, 2008
989
36
Xc, the impedence (resistance) of the capacitor is a function of frequency.

Xc=1/(2*pi*f*C)

Plug in 47 ohms and 10uF and solve for f.

3. ### tegman Thread Starter New Member

Apr 30, 2009
3
0
So I work it like this?

Xc=1/(2*pi*f*c)

2*pi*Xc*c=1/f

f=1/2*pi*47*10*10 -6 power

f=338.62 HZ

4. ### StayatHomeElectronics AAC Fanatic!

Sep 25, 2008
1,021
71
That's exactly the way to do it.

5. ### tegman Thread Starter New Member

Apr 30, 2009
3
0
OK. The load resistor is what was confusing me. I wasnt sure if I should sub. its 47 ohms for Xc in the formula.

Thanks a bunch,
Aron

6. ### StayatHomeElectronics AAC Fanatic!

Sep 25, 2008
1,021
71
The load resistor of 47 ohms is what you were trying to match. It does not have any frequency component to it like a capacitor or inductor so the simple substitution should work.

S@HE

7. ### PRS Well-Known Member

Aug 24, 2008
989
36
StayatHomeElectronics, may I ask what your flag represents?

8. ### StayatHomeElectronics AAC Fanatic!

Sep 25, 2008
1,021
71
It the state flag of Ohio.

When I was working near Pittsburgh I posted one on my wall in my office, it brought a great deal of conversation because I would never tell people what it was. No one ever guessed either.

9. ### PRS Well-Known Member

Aug 24, 2008
989
36
Well, thanks for telling me! I live in Washington state and our flag has George Washington on it, good heavens! I wish the eastern part of our state would seceed from the west and we'd adopt the name Columbia (after the river), and feature Lewis and Clark on our flag. I know ... it ain't gonna happen.

10. ### StayatHomeElectronics AAC Fanatic!

Sep 25, 2008
1,021
71
I never knew there was such division in Washington state! But, I guess we're a little off topic here.