Question

Question 5.10: A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its north tip pointing down at 22º with the horizontal. The horizontal component of the earth’s magnetic field at the place is known to be 0.35 G. Determine the magnitude of the earth’s magnetic field at the place.

Class 12 - Physics - Magnetism And Matter Magnetism And Matter Page-201

Answer 1

North tip is pointing down at 22° with horizontal. hence, the location is in northern hemisphere.
so, angle of dip, $\delta$ =22°
and horizontal components of earth's magnetic field, $B_H$=0.35G

now, $B=\frac{B_H}{cos\delta}$
B = 0.35/cos22° = 0.35/0.927 = 0.38G

hence, magnitude of the earth's magnetic field at the place is 0.38G