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:

$A$ dip needle vibrates in the vertical plane perpendicular to the magnetic meridian. The time period of vibration is found to be $2$ seconds. The same needle is then allowed to vibrate in the horizontal plane and the time period is again found to be $2$ seconds. Then the angle of dip is.....$^o$

When $\sqrt{3} \text{ A}$ current is passed in a tangent galvanometer,there is a deflection of $30^{\circ}$. The deflection obtained when $3 \text{ A}$ current is passed is.....$^{\circ}$

Two magnets are held together in a vibration magnetometer and are allowed to oscillate in the Earth's magnetic field. With like poles of magnets together,$12$ oscillations per minute are made,but for unlike poles together,only $4$ oscillations per minute are executed. The ratio of their magnetic moments is

In a uniform magnetic field,a magnetic needle has a magnetic moment $9.85 \times 10^{-2} \, A \cdot m^{2}$ and a moment of inertia $5 \times 10^{-6} \, kg \cdot m^{2}$. If it performs $10$ complete oscillations in $5 \, s$,then the magnitude of the magnetic field is $.... \, mT$. [ Take $\pi^{2} = 9.85$ ]

The error in measuring the current with a tangent galvanometer is minimum when the deflection is about $45^o$. (in $^o$)