Question

For a cylindrical geometry like a coaxial cable, the capacitance is usually stated as a capacitance per _____.

• A. Unit area
• B. Unit volume
• C. Unit Length
• D. None of these

Answer 1

The correct option is C Unit Length

The capacitance of a cylindrical capacitor of length $l$ and of inner and outer radii $a,b$, is given by:

$C=\frac{2\pi {\epsilon }_{0}l}{{\log }_e\left(b/a\right)}$

$C/l=\frac{2\pi {\epsilon }_0}{{\log }_e\left(b/a\right)}$

For a cylindrical capacitor like a coaxial cable, the capacitance is usually stated as capacitance per unit length. By doing this, capacitance of any length of cable can be measured easily.