A dip needle lies initially in the magnetic meridian when it shows an angle of dip $\theta $ at a place. The dip circle is rotated through an angle $x$ in the horizontal plane and then it shows an angle of dip $\theta '$. Then $\frac{{\tan \theta '}}{{\tan \theta }}$ is
$\frac{1}{{\cos x}}$
$\frac{1}{{\sin x}}$
$\frac{1}{{\tan x}}$
$\cos x$
If the dip circle is set at $45^o$ to the magnetic meridian, then the apparent dip is $30^o$. The true dip. of the place is
The magnetic compass is not useful for navigation near the magnetic poles because
A current carrying coil is placed with its axis perpendicular to $ N-S $ direction. Let horizontal component of earth's magnetic field be $H_o$ and magnetic field inside the loop is $H$. If a magnet is suspended inside the loop, it makes angle $\theta $ with $H$. Then $\theta $$=$
The angle of dip at a certain place is $30^o$. If the horizontal component of the earth’s magnetic field is $H, $ the intensity of the total magnetic field is
A magnetic needle oscillates in a horizontal plane with a period $T$ at a place where the angle of dip is $60^{\circ}$. When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be