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

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SUMMARY

The discussion centers on the calculation of output voltage in a passive RC low pass filter with a resistor value of 22 kΩ and a capacitor value of 100 nF, using an input voltage of 5 Vrms at a frequency of 1 kHz. The key equations involved include UR = R*I, Uout = I*XC, and XC = I / ω*C. A point of contention arises regarding the professor's use of frequency (f) instead of angular frequency (ω = 2πf) in calculations, leading to confusion among students. The consensus is that the professor's notation appears to be a clerical mistake, as standard practice dictates the use of angular frequency in such contexts.

PREREQUISITES
  • Understanding of passive RC low pass filter circuits
  • Familiarity with Ohm's Law (UR = R*I)
  • Knowledge of reactance (XC = 1 / (ω*C))
  • Basic grasp of frequency and angular frequency conversion (ω = 2πf)
NEXT STEPS
  • Study the derivation of output voltage in passive RC filters
  • Learn about the implications of using frequency versus angular frequency in circuit analysis
  • Explore the concept of reactance in AC circuits
  • Review examples of passive filter design and analysis
USEFUL FOR

Electrical engineering students, circuit designers, and anyone studying AC circuit analysis will benefit from this discussion, particularly those focusing on filter design and frequency response.

space5678
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Homework Statement



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 across 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.

94AFb9GrvH3MXwQBm89aUlN8Y3uIzISAg6c_f-yAIpamzl6iDAXYupibtgi9B1d-wFy2QfeLmwWCXhTYH0=w1142-h816-no.jpg


Homework Equations



UR = R*I

Uout = I*XC

XC = I / ω*C

ω = 2*π*f (in rad/s)

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.
 
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Seems wrong to me as well. I got 0.36V.
 
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CWatters said:
Seems wrong to me as well. I got 0.36V.

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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