The electric strength of air is 2.0 x 106 N/C. The largest charge that a metallic sphere of 3 mm radius can hold is

Electric field on the surface of the sphere should not exceed 2.0 x 106 N/C. The electric field on metallic sphere=14πε0×qr2=9×109q3×10−32Hence 9×109q3×10−32=2⋅0×106or     q=2×10−9C=2nC