Q. Two north poles each of pole strength 8Am are placed at corners A and C of a square ABCD. The pole that should be placed at B to make D as null point is
(a)North pole of pole strength 8√2 Am
(b)North pole of pole strength 18√2 Am
(c)North pole of pole strength 4√2 Am
(d)North pole of pole strength 16√2 Am
Ans: (d)