Name the three elements of the Earth's magnetic field and define each. Show how the horizontal and vertical components are related to the angle of dip.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Name the elements. Declination θ, angle of dip δ and the horizontal component B_H.
2 · Define declination. The angle between the magnetic meridian and the geographic meridian at a place.
3 · Define dip. The angle the Earth's total field B makes with the horizontal, in the magnetic meridian.
4 · Draw the components. [In the magnetic meridian: B slanting down at angle δ below the horizontal; B_H along the horizontal and B_V vertically down; δ marked]
5 · Write the relations. B_H = B cos δ and B_V = B sin δ, so tan δ = B_V/B_H and B² = B_H² + B_V².
6 · Link to life. A ship's compass and a phone's compass sensor both respond to the horizontal component.
7 · Close in one line. So, knowing any two of B, B_H, B_V and δ gives the other two.
Scoring tip: When you define dip, add the words 'in the magnetic meridian'. Examiners look for them.
