The law, governing the force between electric charges is known as 

(1) Ampere's law

(2) Ohm's law

(3) Faraday's law

(4) Coulomb's law

F_g and F_e represents gravitational and electrostatic force respectively between electrons situated at a distance 10 cm. The ratio of F_g/ F_e is of the order of 

(1) 10⁴²

(2) 10

(3) 1

(4) 10^–43

A soap bubble is given a negative charge, then its radius 

(1) Decreases

(2) Increases

(3) Remains unchanged

(4) Nothing can be predicted as information is insufficient

Four charges are arranged at the corners of a square ABCD, as shown in the adjoining figure. The force on the charge kept at the centre O is 

(1) Zero

(2) Along the diagonal AC

(3) Along the diagonal BD

(4) Perpendicular to side AB

A total charge Q is broken in two parts Q₁ and Q₂ and they are placed at a distance R from each other. The maximum force of repulsion between them will occur, when 

(1) $Q_2=\frac{Q}{R},Q_1=Q-\frac{Q}{R}$

(2) $Q_2=\frac{Q}{4},Q_1=Q-\frac{2Q}{3}$

(3) $Q_2=\frac{Q}{4},Q_1=\frac{3Q}{4}$

(4) $Q_1=\frac{Q}{2},Q_2=\frac{Q}{2}$  

Three charges 4q, Q and q are in a straight line in the position of 0, l/2 and l respectively. The resultant force on q will be zero, if Q = 

(1) – q

(2) –2q

(3) $-\frac{q}{2}$

(4) 4q

Two small spheres each having the charge +Q are suspended by insulating threads of length L from a hook. This arrangement is taken in space where there is no gravitational effect, then the angle between the two suspensions and the tension in each will be 

(1) ${180}^o,\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{{\left(2L\right)}^2}$

(2) ${90}^o,\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{L^2}$

(3) ${180}^o,\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{2L^2}$

(4) ${180}^o,\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{L^2}$