Question

What is the capacitance of a cylindrical capacitor?

Answer 1

For a cylindrical geometry like a coaxial cable, the capacitance is usually stated as a capacitance per unit length. The charge resides on the outer surface of the inner conductor and the inner wall of the outer conductor. The capacitance expression is

$\frac{C}{L}=\frac{2\pi k{\epsilon }_0}{In\left[\frac{b}{a}\right]}$