Question

At a certain location in Africa, a compass points 12° west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points 60° above the horizontal. The horizontal component of the earth’s field is measured to be 0.16 G. Specify the direction and magnitude of the earth’s field at the location.

Answer 1

Angle of declination, θ = 12°

Angle of dip, δ = 60°

Horizontal component of earth’s magnetic field, B_H = 0.16 G

Earth’s magnetic field at the given location = B

We can relate B and B_H as:

B_H = B cos δ

∴ B = `"B"_"H"/(cos δ)`

= `0.16/(cos 60°)`

= 0.32 G

Earth’s magnetic field lines in the vertical plane, 12° West of the geographic meridian, making an angle of 60° (upward) with the horizontal direction. Its magnitude is 0.32 G.