Question

the magnitude of earths magnetic field at the magnetic north pole is 61/1000000.(a) determine the magnitude of the dipole moment of the earth
(b)suppose an additional field due to the current in wire around the equator is used to make the net field at the pole zero,what is the current?

Answer 1

B =μₒ•I/2•R.
I = 2•R•B/ μₒ.
Dipole moment
p = I•A = (2•R•B/μₒ)•π•R² =2•π•R³•B/ μₒ,
where
μₒ = 4π•10^−7 V•s/(A•m)
R =6.353 •10 ^6 m