Deriving the torque formula for a current loop

[sweatpants]

Homework Statement

If you were given this question: http://img40.imageshack.us/img40/975/picture7we.png
how would you go about solving it?

Homework Equations

I found a formula that makes this question seem a lot easier. Torque = NIAB. however, this formula is not on the formula sheet that is approved by the school so I am not supposed to know about it unless i figure out how to derive it. Does anyone know how this formula was derived?

The Attempt at a Solution

 

[Dick]

Homework Statement

If you were given this question: http://img40.imageshack.us/img40/975/picture7we.png
how would you go about solving it?

Homework Equations

I found a formula that makes this question seem a lot easier. Torque = NIAB. however, this formula is not on the formula sheet that is approved by the school so I am not supposed to know about it unless i figure out how to derive it. Does anyone know how this formula was derived?

The Attempt at a Solution

Try http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magmom.html

 

[sweatpants]

Try http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magmom.html

Hmmm. I've never actually heard of a magnetic dipole moment or its potential energy. Apparently this question is supposed to be solved using solely equilibrium equations and electromagnetism equations which don't already include torque.

Thanks for trying to help though.

 

[OmCheeto]

Hmmm. I've never actually heard of a magnetic dipole moment or its potential energy. Apparently this question is supposed to be solved using solely equilibrium equations and electromagnetism equations which don't already include torque.

Thanks for trying to help though.

Is Force = Current x Length x B-field on your approved formula sheet?

Of course, you'll need to add the equation for torque to come up with the answer.