The true value of angle of dip at a place is $60^o$, the apparent dip in a plane inclined at an angle of $30^o$ with magnetic meridian is
${\tan ^{ - 1}}\frac{1}{2}$
${\tan ^{ - 1}}(2)$
${\tan ^{ - 1}}\left( {\frac{2}{3}} \right)$
None of these
Tell the proper reason for the earth’s magnetic field to occur.
The earth's magnetic field was flipped by $180^{\circ}$ a million years ago. This flip was relatively rapid and took $10^5 \,yrs$. Then, the average change in orientation per year during the flip was closest to ............ $s$
A bar magnet of length $14 \,cm$ is placed in the magnetic meridian with its north pole pointing towards the geographic north pole. A neutral point is obtained at a distance of $18\, cm$ from the center of the magnet. If $B _{ H }=0.4 \,G ,$ the magnetic moment of the magnet is $\left(1\, G =10^{-4} T \right)$
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
Fill in the blank.
$(i)$ The declination is ...... at higher latitudes.
$(ii)$ The declination in India is ...... .