
$H_2$ = Magnetic field at $M$ due to $QR$ + magnetic field at $M$ due to $QS$ + magnetic field at $M$ due to $PQ$
$ = 0 + \frac{{{H_1}}}{2} + {H_1} = \frac{3}{2}{H_1}$
$==>$$\frac{{{H_1}}}{{{H_2}}} = \frac{2}{3}$
Reason : Mass of the electrons is very small
