$A $ magnet freely suspended in a vibration magnetometer makes $10 $ oscillations per minute at a place $A$  and $20 $ oscillations per minute at a place $B$. If the horizontal component of earth’s magnetic field at $A$ is $36 \times {10^{ - 6}}\,T$, then its value at $B$ is

A certain amount of current when flowing in a properly set tangent galvanometer, produces a deflection of $ 45°.$  If the current be reduced by a factor of $\sqrt 3 $, the deflection would

In sum and difference method in vibration magnetometer, the time period is more if

Twists of suspension fibre should be removed in vibration magnetometer so that

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.....$A$

A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of $2\, sec$ in the earth's horizontal magnetic field of $24$ $microtesla$ . When a horizontal field of $18$ $microtesla$ is produced opposite to the earth's field by placing a current carrying wire, the new time period of magnet will be....$s$