Question

two concentric conducting spheres have radii of r1 and r2, with r1 greater than r2. the capacitance is proportional to (r1 - r2)/r1r2, r1r2/(r1 - r2), none of the choices are correct, r2 - r1, r2 + r1

Explanation:

Step1: Recall capacitance formula for concentric spheres

The capacitance $C$ of two - concentric conducting spheres with radii $R_1$ and $R_2$ ($R_1>R_2$) is given by $C = 4\pi\epsilon_0\frac{R_1R_2}{R_1 - R_2}$. So the capacitance is proportional to $\frac{R_1R_2}{R_1 - R_2}$.

Answer:

$R_1R_2/(R_1 - R_2)$