Final answer:
A band-stop filter is created using a combination of a low-pass and high-pass filter. Inductors can act as low-frequency or high-frequency filters depending on whether they replace capacitors in a circuit designed for low or high frequencies, respectively.
Step-by-step explanation:
A band-stop (notch) filter can be designed by using a low-pass filter and a high-pass filter. The combination of these two filters creates a frequency range that the filter will attenuate, effectively 'notching out' or stopping a band of frequencies. This range is between the cut-off frequency of the high-pass filter and the cut-off frequency of the low-pass filter.
Referring to capacitors being replaced by inductors, an inductor will act as a low-frequency filter (also known as a low-pass filter), which allows low-frequency signals to pass and blocks high-frequency signals. Conversely, it will act as a high-frequency filter (also known as a high-pass filter), allowing high-frequency signals to pass and blocking low-frequency signals.
The reason a capacitor can act as a low-frequency filter is due to its impedance decreasing with an increase in frequency. At low frequencies, the impedance is higher, which reduces the signal's ability to pass through. For a high-frequency filter, the impedance of a capacitor is low at high frequencies, allowing those signals to pass through more easily.