A tangent galvanometer has $80$ turns of wire. The internal and external diameters of the coil are $19 \,cm$ and $21 \,cm$ respectively. The reduction factor of the galvanometer at a place where $H=0.32$ oersted will be $(1$ oersted $=80 \,A / m )$

A short bar magnet placed in a horizontal plane has its axis aligned along the magnetic north-south direction. Null points are found on the axis of the magnet at $14\; cm$ from the centre of the magnet. The earth's magnetic field at the place is $0.36\; G$ and the angle of $dip$ is zero.If the bar magnet is turned around by $180^o$, where will the new null points (in $cm$) be located?

A tangent galvanometer has a coil of $25$ $turns$ and radius of $15 \,cm.$ The horizontal component of the earth’s magnetic field is  $3 × 10^{-5}$ $T$. The current required to produce a deflection of $45^o$ in it, is.....$A$

Before using the tangent galvanometer, its coil is set in

The magnetic needle of a tangent galvanometer is deflected at an angle $30^o$ due to a magnet. The horizontal component of the earth's magnetic field is $0.34 \times 10^{-4}\, T$ which is along the plane of the coil. The magnetic field due to magnet is

The ratio of magnetic moments of two bar magnet is $13 : 5$. These magnets are held together in a vibration magnetometer are allowed to oscillate in earth’s magnetic field with like poles together $15$ oscillation per minute are made. What will be the frequency of oscillation of system if unlike poles are together....$oscillations/min$