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?

    I am very lost here:confused: Please help.

    Aron
     
  2. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    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

    Well-Known Member

    Sep 25, 2008
    864
    40
    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

    Well-Known Member

    Sep 25, 2008
    864
    40
    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
    35
    StayatHomeElectronics, may I ask what your flag represents?
     
  8. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    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
    35
    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

    Well-Known Member

    Sep 25, 2008
    864
    40
    I never knew there was such division in Washington state! But, I guess we're a little off topic here.
     
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