posted by Dingleberry .
A friend working on a psychology experiment asks you for help with the design of a simple circuit. She needs an LC timing circuit in which the voltage on a fully charged capacitor drops to zero in 15s . She has a 20H inductor available, but doesn't know what value of capacitor to use. What do you recommend?
The period of charge oscillation will be
P = 2*pi*sqrt(L*C)
In time P/4 , capacitor charge will fall to zero.