Select a capacitor value for your circuit. Many capacitors have nominal values in the microfarad range. The resonant frequency of a band-stop filter depends on two variables: the capacitance of the capacitor and the inductance of the inductor. Since you only have one known value (the frequency), you must select one variable. A 10-microfarad capacitor is a decent choice for a 60 Hz band-stop filter.
Calculate the inductance for the inductor component of the band-stop filter. The resonant frequency equation for such a filter is:
Frequency = 1 / 2 * pi * square root (L*C)
Enter in the known values into the above equation: frequency and capacitance. Use them to solve for the unknown value: inductance (L).
60 Hz = 1 / 2 * pi * square root (L*10*10^-6)
Rearrange the equation so that the unknown value L is on one side of the equal sign, and all the known values are on the other side. You can do this by multiplying both sides of the equation by “2 * pi * square root (L*10*10^-6),” which yields the following result:
2 * pi * square root (L*10*10^-6) * 60 Hz = 1
Isolate the square root on one side of the equation by dividing both sides by “2 * pi * 60 Hz,” which results in the following:
square root (L*10*10^-6) = 1/ (2 * pi * 60 Hz)
Square both sides of the equation to get rid of the square root. The equation now looks like this:
L*10*10^-6 = (1/ (2 * pi * 60 Hz))^2
Solve for L by dividing both sides of the equation by “10*10^-6,” which results in a value of:
L = 703 mH
Order the parts needed for this circuit: one 10-microfarad capacitor and one 703 mH inductor. You may need to order one 700 mH inductor and one 3 mH inductor, if a 703 mH inductor is unavailable.