How Is Torque Calculated in a Circular Coil within a Magnetic Field?

[dgresch]

The maximum torue experienced by a circular, one-turn, coil in a 0.75T magnetic field is 8.4x10^-4Nm. If the coil current is 3.7A, find the coil wire length.

Homework Equations

τ=Fr
F=ILBsinθ ?
r=L

The Attempt at a Solution

(8.4x10^-4Nm)=[(3.7A)L(0.75T)sin90]L
L=0.017m

Can I do this? I don't know how else I'd get the length with the given values.

 

[dgresch]

Never mind, I figured out its just B=u₀NI/2r and I take C=2pie *r to give me length