Magnetism and Matter
9.0 Deflection Magnetometer
9.0 Deflection Magnetometer
It is a device used to determine $M$ and $H.$ Its working is based on tangent law. Deflection magnetometer can be used into two settings
(i) Tangent A setting In this setting the arms of the magnetometer are along east-west and magnet is parallel to the arms.
In equilibrium
$B=H$ $tan$ $?$ $$\frac{{{\mu _o}}}{{\frac{{4\pi 2M}}{{{d^3}}}}} = H\tan \theta $$
(ii) Tangent B setting In this setting the arms of the magnetometer are along north-south and magnet is perpendicular to these arm in equilibrium
$$\frac{{{\mu _o}}}{{\frac{{4\pi M}}{{{d^3}}}}} = H\tan \theta $$
In above setting the experiment can be performed in two ways.
(a) Deflection method In this method one magnet is used at a time and deflection in galvanometer is observed. Ratio of magnetic dipole moments of the magnets $$\frac{{{M_1}}}{{{M_2}}} = \frac{{\tan {\theta _1}}}{{\tan {\theta _2}}}$$ where $?_1$ and $?_2$ are mean values of deflection for two magnets.
(b) Null method In this method both magnets are used at a time and no deflection condition is obtained. If Magnets are at distance $d_1$ and $d_2$ then $$\frac{{{M_1}}}{{{M_2}}} = {\left( {\frac{{{d_1}}}{{{d_2}}}} \right)^3}$$
