At some location on earth the horizontal component of earth's magnetic field is . At this location magnetic of length 0.12 m and pole strength 1.8 Am is suspended from its mid -point using a thread, it makes 450 angle with horizontal in equilibrium . To keep this needle horizontal, the vertical force that should be applied at one of its ends is:
Torque -
T=
- wherein
M - magnetic moment
Resultant Magnetic Field due to earth -
-
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