The membrane of the axon of a nerve cell is a thin cylindrical shell of radius r = 10–5 m, length L = 0.1 m, and thickness d = 10–8 m. The membrane has a positive charge on one side and a negative charge on the other, and acts as a parallel-plate capacitor of area A = 2πrL and separation d. Its dielectric constant is about ? = 3.

(a) Find the capacitance of the membrane. If the potential difference across the membrane is 70 mV, find

(b) The charge on each side of the membrane, and

(c) The electric field through the membrane.