Direction of Torque on Parallel Wires with Current

[Gee Wiz]

Homework Statement

There are two wires in parallel with the current traveling to the left in both. Find the direction of the torque on the top wire due to the bottom wire.

Homework Equations

torque=μ×B

The Attempt at a Solution

I know I can use the right hand rule to find the direction of the b-field using the currents. So, at the top wire the b-field is pointing into the page. I'm not quite sure where μ is here since i thought that only applied to current loops.

 

[tiny-tim]

Hi Gee Wiz!

I know I can use the right hand rule to find the direction of the b-field using the currents. So, at the top wire the b-field is pointing into the page. I'm not quite sure where μ is here since i thought that only applied to current loops.

if you like, you can complete a loop by adding an imaginary third wire, below the bottom wire, with current going to the right, so that you can make a loop out of any section of the top wire and the new wire

 

[Gee Wiz]

So, you mean having the top wire loop with the third bottom wire with the current going in the counterclockwise direction. Then having u point out of the page, and when that is crossed with b the torque would be zero. ?