• # question_answer Explain radial magnetic field. How is it used in moving coil galvanometer?

The magnetic field generated by the two concave poles of magnets is called radial magnetic field as shown in figure. If we place a soft iron cylindrical core between the concave poles, we get magnetic field lines along the radii of circular plane of the cylinder. Use of radial magnetic field in a moving coil galvanometer. The current through a galvanometer coil is             $I=\frac{k}{NAB\sin \theta }\alpha$                              ?(i) Due to this, sin9 term in Eq. (i), the deflection $\alpha$ of the galvanometer is not quite proportional to the current I. So that, the instrument is not a linear one. To make its scale linear, the field is made radial. Then, $\theta =90{}^\circ ,$ so that             $I=\frac{k}{NBA}\alpha$ Thus,    $I\propto \alpha$