Answer : They are inversely proportional to the square of the distance.
Explanation :
We know that the electrical or electrostatic force is given by :
.........(1)
Where,
is constant
are the electric charges,
r is the distance between two charges.
Similarly, the gravitational force is given by :
..........(2)
Where
G is the universal gravitational constant
and
are the masses
r is the distance between them
From equation (1) and (2), it is clear that the both electrical as well as gravitational forces are inversely proportional to the square of the distance between them.
Hence, the correct option is (b) " They are inversely proportional to the square of the distance" .