The earth’s magnetic dipole moment is 8.0 × 10²² A m².
a. What is the magnetic field strength on the surface of the earth at the earth’s north magnetic pole? How does this compare to the value in Table 29.1? You can assume that the current loop is deep inside the earth.
b. Astronauts discover an earth-size planet without a magnetic field. To create a magnetic field at the north pole with the same strength as earth’s, they propose running a current through a wire around the equator. What size current would be needed?

Table 29.1

Field source......................Field strength (T)

Surface of the earth ..........5 × 10^-5

Refrigerator magnet .........5 × 10^-3

Laboratory magnet ............0.1 to 1

Superconducting magnet .......10