Question

Two point charges +Q and +4Q are placed at a distance "a" apart on a horizontal plane . where should the third charge be placed for it to be in equilibrium ​

Answer 1

if two like charge then third charge is placed b/w the line joining and inside and close to small magnitude of charge let x distance from +Q a q charge is placed and a-x from+4Q then for eq. f net equal k qQ/x^2=kq4Q/(a-x)^2 then after solving 2x=a-x then x=a/3