Two equal charges are saperated by a distance d A third charge place on a perpendicular bisector at x distance will experience maximum coloumb force when

Dear pallavi

F= k qQ/x²

   horizontal component of this force will cancel each other and verticle component will be added

net force F'=2Fcosθ

                cosθ = (x²-d²/4)^1/2/x

  so F' = 2kqQ(x²-d²/4)^1/2/x³

           for maximum force differential and put equal to zero

x= √3 d/4

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