Q.
Capacitance of an isolated conducting sphere of radius R1 becomes n times when it is enclosed by a concentric conducting sphere of radius R2 connected to earth. The ratio of their radii (R1R2) is:
Capacitance of isolated Conducting sphere =4πε0R1
By enclosing inside another sphere of radius R2, new capacitance =(R2−R1)4πε0R1R2
Given : (R2−R1)4πε0R1R2=n×4πε0R1 ⇒(R2−R1)R2=n⇒(R1R2−1)R1R2=n ⇒R1R2=nR1R2−n⇒R1R2=(n−1)n