Four charges $Q_{1}, Q_{2}, Q_{3}$ and $Q_{4}$ of same magnitude are fixed along the $x$ axis at $x = - 2 a, - a, + a$ and $+ 2 a,$ respectively. $A$ positive charge $q$ is placed on the positive $y$ axis at a distance $b > 0 .$ Four options of the signs of these charges are given in List I. The direction of the forces on the charge $q$ is given in List II. Match List I with List II and select the correct answer using the code given below the lists.

List I List II

P. $Q_{1}, Q_{2}, Q_{3}, Q_{4}$ all positive 1. $+ x$

Q. $Q_{1}, Q_{2}$ positive; $Q_{3}, Q_{4}$ negative 2. $- x$

R. $Q_{1}, Q_{4}$ positive; $Q_{2}, Q_{3}$ negative 3. $+ y$

S. $Q_{1}, Q_{3}$ positive; $Q_{2}, Q_{4}$ negative 4. $- y$

Question

Important Questions on Coulomb's Law and Electric Field