At a certain place,a magnet makes $30$ oscillations per minute. At another place where the magnetic field is double,its time period will be:

Two tangent galvanometers having coils of the same radius are connected in series. $A$ current flowing in them produces deflections of $60^{\circ}$ and $45^{\circ}$ respectively. The ratio of the number of turns in the coils is

Two tangent galvanometer coils of the same radius are connected in series. The current flowing produces deflections of $60^o$ and $45^o$. The ratio of the number of turns in the coils is:

In the sum and difference method of a vibration magnetometer,the time period is greater if:

The needle of a deflection galvanometer shows a deflection of $60^\circ$ due to a short bar magnet at a certain distance in $\tan A$ position. If the distance is doubled,the deflection is

$A$ short magnet oscillates with a frequency $10 \, Hz$ where the horizontal component of Earth's magnetic field is $12 \, \mu T$. $A$ downward current of $15 \, A$ is established in a vertical wire placed $20 \, cm$ west of the magnet. The new frequency of the magnet is (in $ \, Hz$)