Question

Please help. I'm having a hard time understanding these magnetic force/field problems :/

Answer 1

The earth’s magnetic field, with a magnetic dipole moment of 8.0 * 1022 A m2, is generated by currents within the molten iron of the earth’s outer core. Suppose we model the core current as a 3000-km-diameter current loop made from a 1000-km-diameter “wire.” The loop diameter is measured from the centers of this very fat wire.

a. What is the current in the current loop?
b. What is the current density J in the current loop?
c. To decide whether this is a large or a small current density,
compare it to the current density of a 1.0 A current in a

Is there like an expression for magnetic dipole moment? I can't find it in my textbook or online.

Answer 2

If your notes are failing you, you'll find a good resource on Wiki

but best quick-look reference usually is Hyperphysics

Answer 3

Ohh cool I got it, u= IA, where u is magnetic dipole moment, i is current, and A is area of loop. :) Thanks