Balancing magnetic forces on rods

[Will Freedic]

Homework Statement

If two parallel rods are placed 1mm apart, with one directly above the other, each carrying a current I in opposite directions, of length L what is the mass of the upper rod as to balance the force

Homework Equations

F=ILxB[/B]

The Attempt at a Solution

I have little idea of how to go about attempting this solution, thankyou! [/B]

 

[Herman Trivilino]

You need to assume the lower wire is held in a fixed position. It exerts a magnetic force $IL\times B$ on the upper wire.

 

[Will Freedic]

You need to assume the lower wire is held in a fixed position. It exerts a magnetic force $IL\times B$ on the upper wire.

Thankyou, but how do you work the magnetic field strength?

 

[cnh1995]

Thankyou, but how do you work the magnetic field strength?

Biot-Savart's law or Ampere's law will be useful here.

 

[Herman Trivilino]

Thankyou, but how do you work the magnetic field strength?

I suggest you look in a textbook. There should be a section on force between long parallel current-carrying wires.