12th Class Physics Sample Paper Physics Sample Paper-9

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

    Answer:

    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,    \[I\propto \alpha \]


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