
But magnetic field at $\mathrm{M}$ due to $\mathrm{QR}=0$
Now $\quad \mathrm{H}_{2}=$ Magnetic field at $\mathrm{M}$ due to $\mathrm{PQ}$ (cument $\mathrm{I}$ )
$+$ Magnetic field at $M$ due to $QS$ (current $1/2$)
$+$ Magnetic field at $M$ due to $QR$
$=\mathrm{H}_{1}+\frac{\mathrm{H}_{1}}{2}+0=\frac{3}{2} \mathrm{H}_{1}$
$\therefore \quad \frac{\mathrm{H}_{1}}{\mathrm{H}_{2}}=\frac{2}{3}$
Magnetic field at any point lying on the current carrying straight conductor is zero.
$(A)$ If $I_1=I_2$, then B' cannot be equal to zero at the origin $(0,0,0)$
$(B)$ If $\mathrm{I}_1>0$ and $\mathrm{I}_2<0$, then $\mathrm{B}$ can be equal to zero at the origin $(0,0,0)$
$(C)$ If $\mathrm{I}_1<0$ and $\mathrm{I}_2>0$, then $\mathrm{B}$ can be equal to zero at the origin $(0,0,0)$
$(D)$ If $\mathrm{I}_1=\mathrm{I}_2$, then the $\mathrm{z}$-component of the magnetic field at the centre of the loop is $\left(-\frac{\mu_0 \mathrm{I}}{2 \mathrm{R}}\right)$
