23.
An RL low-pass filter consists of a 5.6 mH coil and a 3.3 kΩ resistor. The output voltage is taken across the resistor. The circuit's critical frequency is

28.
A parallel resonant band-pass filter consists of a 90 Ω resistor in series with a parallel network made up of a 60 mH coil and a 0.02 µF capacitor. The output is taken across the capacitor/coil. The coil winding has a resistance of 20 Ω. What is the center frequency of the filter?

29.
A parallel resonant band-pass filter consists of a 6.8 Ω resistor in series with a parallel network made up of an 8 µH coil and a 120 pF capacitor. The output is taken across the capacitor/coil. Assume RW = 0 Ω. What is the center frequency of the filter?