I don’t understand why parallel wires with current running in the same direction attract. enter image description here

Wire 1 on the left, per the right hand rule, should cause wire 2 to experience a leftwards force. Wire 2 on the right, should cause wire 1 to experience a leftwards force as well. Shouldn’t they both be going to the left, never really meeting each other. When I think of attraction, I think of force vectors pointing inwards like so: —> <— , not pointing in the same direction like so: <— <—

What am I missing here? How do these two wires meet each other if they are both being pushed with equal forces (?) in the same direction. Does one wire exert a greater force than the other, all else being equal? If so, how could this be? When I watch video explanations of this problem, I typically see force vectors and magnetic field lines drawn out for only one of the two wires—this confuses me to no end.

I've spent several hours wrestling with this problem and would greatly appreciate some help untying this knot.


1 Answer 1


The following may be useful. The $B$-field from wire 1 (on the left) points into the page of the diagram at the position of wire 2. Conversely, the $B$-field from wire 2 points out of the page at the position of wire 1. Since the currents are both going up as shown, the force on wire 1 is to the right, and the force on wire 2 is to the left.

I hope this helps.

  • $\begingroup$ This is perfect, thank you very much! I just wasn't thinking of the field lines correctly. $\endgroup$
    – Beowulf
    Nov 19, 2020 at 22:19

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