Chapter 28, Problem 76PP

A filter is a circuit designed to pass AC signals in some frequency range and to attenuate others. Common filters include low-pass filters, which allow low-frequency signals to pass but attenuate high frequencies; high-pass filters, which do the opposite; and band-pass filters, which pass a range of frequencies while attenuating signals with frequencies outside the band. Filters are widely used in electronics. Applications include tone and equalizer controls in audio equipment; filters to separate nearby frequencies at cell phone towers; and filters to eliminate unwanted electrical noise in biomedical instruments such as electrocardiographs. A simple design for an RC filter is shown in Fig. 28.27.

Figure 28.27 An RC filter (Passage Problems 73–76)

If you replace the capacitor in Fig. 28.27 with an inductor, the circuit

1. a. continues to function as before.
2. b. becomes the opposite kind of filter.
3. c. produces zero output voltage because the inductor is a short circuit.
4. d. produces an output voltage that exceeds the input voltage.