Why do parallel wires with identical currents attract each other?

[hiljd]

Homework Statement

Not too difficult really, but I'm not understanding why two wires with identical currents running through them will move together. The question is, 'what happens when two parallel wires carry identical currents in oppsite directions?' But I don't understand what happens when they carry them in the same direction, so can't atempt this question.

Homework Equations

The Attempt at a Solution

 

[berkeman]

Thread moved from Advanced Physics to Intro Physics.

Start by drawing the magnetic field that circulates around the wire axis for each wire. Now, the electrons that are moving in a nearby wire will be affected by that circulating magnetic field in what way? Remember to use the right-hand rule to figure out the direction of the force on the moving electron charges in the magnetic field.

 

[JK423]

The following will probably help you:
1)Ampere`s law
2)Laplace force + Right-hand rule

 

[turdferguson]

http://www.physics4students.com/pages/dataDump/rightHandRule.jpg
Take a look at the top picture. The magnetic field at a point to the right of the wire points into the screen. A bar magnet would have its north pole into the screen and its south pole out of the screen. If an identical second wire is placed to the right of that, its field would point into the screen. A bar magnet to the left of the second wire would have its south pole into the screen and its north pole out of the screen. Now we have 2 magnets arranged north-south and south-north, which will attract each other