Two identical thin bar magnets each of length l and pole strenght m are placed at right angles to each other with north pole of one touching south pole of the other . Magnetic moment of the system is

Explanation

As magnetic moment is a vector
`M_(R) =(M_(1)^(2) + M_(2)^(2)+2 M_(1)M_(2)costheta)^(1/2)`
with `tan phi = M_(2)sin theta/M_(1)+M_(2)cos theta`
and as here `M_(1)=M_(2)=mL`and `theta=90^(@)`,so
`M_(R)=(M^(2)+M^(2)+2MMcos 90^(@))1//2=(sqrt(2))mL`
`:. Tan^(-1)(1)=45^(@)`