Earth has a magnetic dipole moment of 8.0 × 1022 J/T. (a) What current would have to be produced in a single turn of wire extending around Earth at its geomagnetic equator if we wished to set up such a dipole? Could such an arrangement be used to cancel out Earth's magnetism (b) at points in space well above Earth's surface or (c) on Earth's surface?

a

The current that would be produced is

b

Yes this arrangement can be used to cancel out earths magnetic field at points well above the Earth's surface.This is because this current loop acts as a magnetic dipole for point above the earth surface  

c

No this arrangement can not be used to cancel out earths magnetic field at points on the Earth's surface .this because on the earth surface it shifts from its behavior as a magnetic dipole

Explanation:

    From the question we are told that

             The magnetic moment of earth is

               The radius of earth generally has a value of

Magnetic moment is mathematically given as

A is the area of the of the earth(assumption that the earth is circular ) and this evaluated as  

Now making the subject in the above formula

d is the answer i came up with

the independent variable, or the one that is intentionally manipulated is the speed.