A cylindrical capacitor consists of a solid inner conducting core with radius 0.200cm , surrounded by an outer hollow conducting tube. The two conductors are separated by air, and the length of the cylinder is 11.5cm . The capacitance is 35.5pF.
a) Calculate the outer radius of the hollow tube.
b) When the capacitor is charged to 140v , what is the charge per unit length on the capacitor?