our teacher asked a conceptual question. Let two infinite straight wires carrying current in the same direction be suspended in vacuum near each other. the wires tend to get attracted due to the lorentz force. but since work done by lorentz force must be zero, there should not have been kinetic energy. the question is what agent actually performs the external work to produce a change in kinetic energy of wires?
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$\begingroup$ see these physics.stackexchange.com/questions/640881/… and physics.stackexchange.com/questions/412403/… $\endgroup$– hyportnexCommented Jun 25 at 14:26
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$\begingroup$ In short, the force $\mathbf F = q\mathbf{v \times B}=\mathbf {j\times B}$ indeed does no work in the direction of $\mathbf j$ because $\mathbf F$ is perpendicular to $\mathbf j$ but it can and will exert force and does work in any other direction not along the current itself, here specifically perpendicular to the kinematic constraint caused by electric conductivity that forces the current to move along with the wire. $\endgroup$– hyportnexCommented Jun 25 at 14:41
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