A long cylindrical capacitor consists of a solid conducting core with a radius of r$\_($a$)$ and an

outer hollow conducting tube with an inner radius of r$\_($b$).$ The two conductors are separated

by air and charged to a potential difference V$.$ The charge per length for the capacitor is $\backslash$Lambda $.$

What is V $?$

A$.\backslash$lambda ln$(($r$\_($b$))/($r$\_($a$)))/(3)\backslash$pi $\backslash$epsi $\_(0)$

B$.\backslash$lambda ln$(($r$\_($b$))/($r$\_($a$)))/(2)\backslash$pi $\backslash$epsi $\_(0)$

C$.\backslash$lambda ln$(($r$\_($b$))/($r$\_($a$)))/(\backslash$pi $)\backslash$epsi $\_(0)$

D$.\backslash$lambda ln$(($r$\_($b$))/($r$\_($a$)))/(4)\backslash$pi $\backslash$epsi $\_(0)$