Q 1.1) What is the force between two small charged spheres having charges of 2 × 10–7C and 3 × 10–7 C placed 30 cm apart in the air?

 
Repulsive force of magnitude = 6 x 10-3 N
Charge on the first sphere, q1= 2 x 10-7 C
Charge on the second sphere, q2 = 3 x 10-7CDistance between the spheres, r = 30 cm = 0.3 m

The electrostatic force between the spheres:F=14πε0q1q2r2Where E = Permittivity of free space and 14πε0=9×109Nm2C2
Therefore, forceF=9×109×2×107(0.3)2=6×103NHence, the force between the two small charged spheres is 6 x 10-3 N. The charges are of the same nature. Hence, the force between them will be repulsive.