# Electrical Engineering - Passive Filters - Discussion

### Discussion :: Passive Filters - General Questions (Q.No.2)

2.

An RL low-pass filter consists of a 5.6 mH coil and a 3.3 k resistor. The output voltage is taken across the resistor. The circuit's critical frequency is

 [A]. 93.8 kHz [B]. 93.8 Hz [C]. 861 Hz [D]. 86.12 kHz

Explanation:

No answer description available for this question.

 Shrutali said: (Sep 1, 2011) How to find critical frequency in this problem ?

 Asha said: (Oct 15, 2011) Critical frequency=R/2*PIE*L

 Shankarling.Patil said: (Apr 27, 2012) What is critical frequency. Please tell me friends.

 Naga Mallesh said: (Jul 27, 2012) When R = XL its called critical frequency.

 Shahul said: (Apr 5, 2013) Critical frequency/Bandwidth = R/ (2*3. 14*L).

 Jon said: (Sep 22, 2013) Using R = XL. Then R = 2*pie*freq*L. Freq. = R/(2*pie*L). = 3300/(2*3.1416*.0056). Freq. = 93,787 Hz or 93.8 KHz.

 Pesce said: (Apr 26, 2015) Critical frequency is a frequency at which I is maximum in RLC circuit. i.e, when R=sqrt (XL*XL-Xc*Xc). Here, Xc = 0 (since RC ckt). So. R = XL. But XL = 2*pie*f*L. Hence R = 2*pie*f*L. F = R/2*pie*L.

 Mshal said: (Feb 15, 2016) At Resonant state of series RLC circuit, Z = R = (XL-XC). Since R & L are given, R = XL but XL = 2*π*F*L. Therefore 3.3k ohms = 2*3.1416*F*5.6 millihenry; F = 93.78 HZ.

 Sana said: (Jul 8, 2016) Is critical and cut off frequency are same?

 Sonu Kumar said: (Apr 1, 2018) F =R/2πL, = 3300/2*3.14*.0056, = 3300/6.28*.0056, = 33*10^8/628*56, = 33*10^8/35168, = 93835hz or, = 93.8khz.

 Haris said: (Jan 6, 2020) No, @SANA. Critical frequency is the highest magnitude of frequency above which the waves penetrate the ionosphere and below which the waves are reflected back from the ionosphere. Ionosphere: The layer of the earth's atmosphere which contains a high concentration of ions and free electrons and is able to reflect radio waves. CUT OFF FREQUENCY: It is a level above or below at which the system fails to operate.