# Straight wires carrying DC currents

## Main Question or Discussion Point

Straight wires carrying DC currents....

Dear Forum,

when will two straight wires, both carrying a DC current, not feel any mutual magnetic force?

What reciprocal orientation do they need to have? It looks to me that they will always feel a magnetic force if they are parallel, perpendicular or at any other angle, since they are immersed in each other B field which is not parallel to the wire direction......is that true?

But I have been told that if they are infinite and perpendicular, there will be no net force....
Why? Net force in the sense that there are two forces that oppose each other, or no force on either wire?

thanks,
fisico30

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I think the magnetic force depends on the direction of the current in each wire... if the wires are carrying currents in the same direction they attract each other, but if they carry currents in the opposite direction then the force between them is repulsive. So the net force depends on whether the currents are parallel or anti-parallel.

Matterwave