Practice portal › Magnetism and Matter › Bar Magnet and Dipole in a Field
Asked in AIPMT 2012 · Field of a bar magnet and earth's field
Idea: a compass needle is turned by the horizontal component of the earth's field, B_H.
At a geomagnetic pole the angle of dip is 90°, so the field points straight down.
Then B_H=B cos 90°=0.
With no horizontal component there is no torque about the vertical axis the needle turns on.
So the needle has no preferred direction in the horizontal plane and rests wherever it is put.
Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.
Practise this with a timer