Question

Three positive charges of equal magnitude q are placed at the vertices of and equilateral triangle of side l. How can the system of charges be placed in equilibrium?
A. `1:3`
B. `1:sqrt(3)`
C. `sqrt(3):1`
D. `2:sqrt(3)`

Answer 1

Correct Answer - B
Net force on q will be zero for any value of q and Q. Net force on each Q should also be zero. For this q should be negative of Q.

`F_(2)=2F_(1) cos 30^(@)`
or, `(kqQ)/((a//sqrt(3))^(2))=2(kQ^(2))/(a^(2)) (sqrt(3))/(2) or q/Q=1/(sqrt(3))`.