Question

Six charges, three positive and three negative of equal magnitude are to be placed at the vertices of a regular hexagon such that the electric field at O is double the electric field when only one positive charge of same magnitude is placed at R Which of the following arrangements of charge is possible for, P, Q, R, S, T and U respectively ?

• A. +,-,+,-,-,+
• B. +,-,+,-,+,-
• C. +,+,-,+,-,-
• D. -,+,+,-,+,-

Answer 1

Answer: (D)

-,+,+,-,+,-

Answer 2

According to option (d) the electric field due to P and S and due to Q and T add to zero. While due to U and R will be added up. Hence, the correct option is (d).
(P) Component of forces along x-axis will vanish.
Net force along positive 7-axis
\hspace15mm E_3 < E_1 < E_2
(Q) Component of forces along 7-axis will vanish. Net force along positive x-axis
(R) Component of forces along x-axis will vanish. Net force along negative 7-axis
(S) Component of forces along 7-axis will vanish. Net force along negative x-axis