When the knob of a certain radio tuning capacitor is turned, the effective area of the plates in the interleaved position is reduced from 40 cm^2 to 10cm^2.
A. What is the ratio of initial to the final capacitance?
B. If the initial capacitance is 1 uF, what is the plate seperation?
C. What is the new capacitance when the area is 10 cm^2?
D. If the radio is powered by a 9 volt battery, what are the initial and final charges on the plates?