Quick question about magnetic fields

[BrooklynBees]

Homework Statement

The force on a wire .80 m long that is perpendicular to the Earth's magnetic field is .12 N. What current flows throught the wire? (Earth's magnetic field is 1.0x10^-4 T at the poles and 5.0x10^-5 T at the equator)

Homework Equations

Fm=BIl
Fm is magnetic force in N, B is magnetic field strength in telsa (T), and l is length in meters.

The Attempt at a Solution

I'm just not sure what I'm supposed to use for B. Do I use the strength at the poles? at the equator? Some combination of the two?

Thanks.

 

[dynamicsolo]

This certainly is a mysterious problem statement: doesn't it say anything about where on Earth the wire is? Maybe you're supposed to find the range of possible values for the current within the range of values for the local magnetic field strength. Since we're told that the wire is perpendicular to the local field, the "magnetic dip angle" (angle the field makes to the local horizontal) doesn't matter. It seems like there's something left out of the problem...

 

[Moetasim]

I would suggest using the average magnetic field strength between the poles and the equator, which would be (1.0x10^-4 + 5.0x10^-5)/2 = 7.5x10^-5 T. This will provide a more accurate calculation for the current flow through the wire. Additionally, it is important to note that the direction of the current flow will depend on the direction of the Earth's magnetic field. If the wire is perpendicular to the field, the current will flow parallel to the ground. If the wire is parallel to the field, the current will flow perpendicular to the ground.