Question

Two metallic spheres of radii $1\text{cm}$ and $3\text{cm}$ are given charge of $-1\times {10}^{2}C\text{and}5\times {10}^{2}C$ respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is

• A. $4\times {10}^{2}C$
• B. $1\times {10}^{2}C$
• C. $2\times {10}^{2}C$
• D. $3\times {10}^{2}C$

Answer 1

The correct option is D $3\times {10}^{2}C$

Let $q_1,q_2$ be charges on spheres,
Total charge on spheres is $q_1+q_2=4\times {10}^2$

Charge on both spheres after contact
$\frac{q_1}{q_2}=\frac{R_1}{R_2}=\frac{1}{3}$

Charge on bigger sphere $q_2=\frac{3}{4}\times 4\times {10}^2=3\times {10}^{2}C$