Question

Two current-carrying wires may attract each other. In absence of other forces, the wires will moves towards each other increasing the kinetic energy. Does it contradict the fact that the magnetic force cannot do any work and hence cannot increase the kinetic energy?

Answer 1

Explanation:

• Magnetic field can never speed down or speed up a particle because it cannot do any work.  
• Let’s consider two wires traversing current in the upward direction. In wire 1, the magnetic field creates a magnetic field from the paper plane at the position of the second wire.
• It should be observed that there is an exertion of force on wire 2 due to the magnetic field. The electron of wire 2 moving the downward direction, moves in circular paths because of the magnetic force.  
• These electrons cannot move out of the wire. Hence, while explaining the circular path, these electrons hit the wire edges and a momentum to the wire is transferred.
• Because of this momentum, the wire gains kinetic energy as it starts moving.