A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its north tip pointing down at 22° 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.

Question

Philoid · Accepted Answer

Horizontal component of earth’s magnetic field, B_H = 0.35 G

Angle made by the needle with the horizontal plane = Angle of dip = δ 22°

Earth’s magnetic field strength = B

We know, B_H = B cosδ

B = B_H/cos δ = 0.35/(cos 22^o) = 0.377 G

The strength of earth’s magnetic field at the given location is 0.377 G.