Q. Two concentric circular coils $X$ and $Y$ of radii $16cm$ and $10cm,$ respectively, lie in the same vertical plane containing the north to south direction. Coil $X$ has $20$ turns and carries a current of $16A$ ; coil $Y$ has $25$ turns and carries a current of $18A$ . The sense of the current in $X$ is anticlockwise, and clockwise in $Y,$ for an observer looking at the coils facing west. The magnitude of the net magnetic field due to the coils at their centre is :-
NTA AbhyasNTA Abhyas 2020
Solution: