Minimum Current for Magnetic Levitation: Is It Safe for a Magician's Act?

[w3390]

Homework Statement

Your friend wants to be a magician and intends to use Earth's magnetic field to suspend a current-carrying wire above the stage. He asks you to estimate the minimum current needed to suspend the wore just above Earth's surface at the equator (where the Earth's magnetic field is horizontal). Assume the wire has a linear mass density of 10g/m. Would you advise him to proceed with his plans for this act?

Homework Equations

dF=IdlxB, where dlxB is a cross product

The Attempt at a Solution

I am having trouble understanding where to start. I am having trouble visualizing the problem and I don't know how to incorporate the linear mass density into anything. My book does not go over anything like this. Help on how to start would be much appreciated.

 

[LowlyPion]

You will first need to find the magnetic field strength at the equator.
http://en.wikipedia.org/wiki/Earth's_magnetic_field

Then:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html#c1

 

[w3390]

I do not understand how to get I from the equations in your second link. I understand what they mean and I have used them a lot, but I am not sure how the force is going to come into play.

 

[LowlyPion]

I do not understand how to get I from the equations in your second link. I understand what they mean and I have used them a lot, but I am not sure how the force is going to come into play.

Well it will take real magic then to suspend a wire.

If the qV got you then try

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/forwir.html#c1

 

[w3390]

Thank you so much. That last link does an amazing job at helping the visualization process. Once I could see what was happening, it made complete sense.