The magnetic dipole moment of the Earth is . We may assume that this is produced by charges flowing in the molten outer core of the Earth and that the radius of the circular path is 3500 km. We have to calculate the required current.

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The magnetic dipole moment of a current carrying closed planar loop is

,

where is the current flowing in the loop and is the area enclosed by it.

As the magnetic dipole moment of the Earth,

, and the area enclosed by the current loop

,

the required current