First slide
Magnetism
Question

The magnetic moment of the assumed dipole at the earth’s centre is  7.0×1022Am2. The magnetic field B at the geomagnetic poles of the earth  is P×1014R3 (The radius of earth is ‘R’), then the value of ‘P ’ is__ 

Moderate
Solution

The geomagnetic pole is at the end on position of the earth (axial position)  B=μ04π.2Md3

given  : d=R B=107×2×7×1022R3=14×1015R3

Hence, 

P×1014R3=14×1015R3 P=140.00

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