# Homework Help: Earth's Magnetic Dipole Moment

1. Mar 21, 2014

### majormaaz

1. The problem statement, all variables and given/known data
The earth's magnetic dipole moment is 8.0 x 1022 A m2.

(a) What is the magnetic field strength on the surface of the earth at the earth's north magnetic pole? You can assume that the current loop is deep inside the earth. 6.17e-5 T

(b)How does this compare to 5.0 x 10-5 T, the typical field strength on the surface of the earth?
1.23 times the typical field strength

(c)Astronauts discover an earth-size planet without a magnetic field. To create a magnetic field, so that compasses will work, they propose running a current through a wire around the equator. What size current would be needed? (Give the current necessary to produce a magnetic dipole equal to the earth's.)

2. Relevant equations
Bloop = (μ0/4∏)*(2AI/z3) --> on-axis magnetic field of a current loop/.
AI = magnetic dipole moment μ

3. The attempt at a solution
I'm confused as what to do, as it says to find a current necessary to produce a magnetic dipole, whereas the only term I'm familiar with in the context of this problem is the magnetic dipole moment AI. If someone could help me clarify which term I should be focusing on so that I can use the appropriate equation, that'd be great.

2. Mar 21, 2014

### paisiello2

I think you might be overcomplicating part c). I would look at how the magnetic dipole is defined/derived and substitute the values in directly.

3. Mar 21, 2014

### majormaaz

Yeah, I got the right answer. Basically, I was confused whether the magnetic dipole moment was the same thing as the magnetic dipole or not, but it turns out it is. Thanks!