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Homework Help: Low Pass: Why did my professor use frequency and not angular frequency?

  1. Apr 14, 2017 #1
    1. The problem statement, all variables and given/known data

    We are given a passive RC low pass filter with an input voltage of 5 Vrms at a frequency of 1 kHz. The resistor has a value of 22 kΩ, the capacitor a value of 100 nF. There is a current i accross the resistor. (see picture below)

    We are to calculate the magnitude and phase angle of the output voltage.

    By the way, in the picture below is in german, so V eff means rms, I think the rest should be apparent.


    2. Relevant equations

    UR = R*I

    Uout = I*XC

    XC = I / ω*C

    ω = 2*π*f (in rad/s)

    3. The attempt at a solution

    Analytically, this is not a problem, and I have attached the solution from the professor. My only problem is that for ω the professor used the frequency f, and not 2πf. As in:

    ω = f = 1 kHz

    This makes no sense to me and seems wrong. Could somebody possibly clarify what´s going on here? Thanks in advance.
  2. jcsd
  3. Apr 14, 2017 #2


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    Seems wrong to me as well. I got 0.36V.
  4. Apr 15, 2017 #3
    I think this must be a clerical mistake, as in all of the other examples he uses ω = 2πf. Thanks a bunch for checking! :oldsmile:
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