Practice portal › Magnetism and Matter › Bar Magnet and Dipole in a Field
Asked in RS Academy GUJCET booklet · Field of a bar magnet and earth's field
Idea: with δ the angle of dip, the two components of the Earth's field are B_H=B cos δ and B_V=B sin δ.
B_H=0 needs cos δ=0, that is δ=90°: the field must point straight down (or straight up).
The dip is 90° at the geomagnetic poles, the two points where the Earth's magnetic axis meets the surface; a dip needle there stands vertical and a compass is useless.
At the geomagnetic equator the opposite holds: δ=0, the field is horizontal and B_V=0.
So the horizontal component is zero at one of the geomagnetic poles.
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