Answer:
C. [tex]\frac{3F}{8}[/tex]
Explanation:
Let initial charges on both spheres be,[tex]q[/tex]
[tex]F=\frac{Kq^2}{d^2} \ \ \ \ \ \ \ \ \ \ \_i[/tex]
When the sphere C is touched by A, the final charges on both will be,[tex]\frac{q}{2}[/tex]
#Now, when C is touched by B, the final charges on both of them will be:
[tex]q_c=q_d=\frac{q/2+q}{2}\\\\=\frac{3q}{4}\\[/tex]
Now the force between A and B is calculated as:
[tex]F\prime=\frac{k\times\frac{q}{2}\times \frac{3q}{4}}{d^2}\\F\prime=\frac{3F}{8}[/tex]
Hence the electrostatic force becomes 3F/8
