current in a wire

[orangetea]

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Suppose you have two wires(laid down flat like this --> | | )

In one current is moving upwards

In another current is moving down.

Do these wires repel or attract each other and why?

It is from TBR I just can't remember the page.. (not written in my notes fml) 😀

 

[JMMTB]

Wires carries currents in opposite directions always repel. Same direction attract.

The force acting on a current carrying wire is given by F=ILB
The magnetic field (B) created by a wire can be found by using the right hand rule. In this case point your thumb in the direction of the current (up or down) and your fingers will curl in the direction of B.

So for convention if we say the left wire is carrying current UP and the right DOWN then we find that the Magnetic field between them is INTO the screen.

To then find the force acting on the wire we then use F=ILB where it is I cross B to get the correct direction. So for the left wire we place our right palm in the direction of current (up facing away from us) then we turn our fingers in the direction of the magnetic field that comes from the OTHER wire (into the screen) now our thumb points in the direction of the force (to the left). If we follow this for the right wire we find that it feels a force to the right.

Thus the two wires repel each other.