Answer:
8 N
Explanation:
The force between two charges is given by :
[tex]F=\dfrac{kq_1q_2}{d^2}[/tex]
Where
k is electrostatic constant
d is the distance between two charges
It means,
[tex]F\propto \dfrac{1}{d^2}[/tex]
When the distance is d, the force is 2 N. If the charge on each sphere is doubled, q₁' = q₂' = 2q₁ = 2q₂. New force will becomes:
[tex]F'=\dfrac{kq_1'q_2'}{d^2}\\\\F'=\dfrac{k2q_1\times 2q_2}{d^2}\\\\F'=4\times \dfrac{kq_1q_2}{d^2}\\\\F'=4\times 2\\\\F'=8\ N[/tex]
So, the new force becomes 8N. Hence, the correct option is (d).