A magnetic needle is made to vibrate in uniform field $H$, then its time period is $T$. If it vibrates in the field of intensity $4H, $ its time period will be

Tangent galvanometer is used to measure

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….$s$

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

$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