The dipole moment of a circular loop carrying a current I, is m and the magnetic field at the centre of the loop is B_1. When the dipole moment is…

The dipole moment of a circular loop carrying a current I, is m and the magnetic field at the centre of the loop is $\displaystyle \mathrm{B}_1$. When the dipole moment is doubled by keeping the current constant, the magnetic field at the centre of the loop is $\displaystyle \mathrm{B}_2$. The ratio $\displaystyle \frac{\mathrm{B}_1}{\mathrm{~B}_2}$ is :