Two bar magnets are placed close to each other with their opposite poles facing each other. In absence of other forces, the magnets are pulled towards each other and their kinetic energy increases. Does it contradict our earlier knowledge that magnetic forces cannot do any work and hence cannot increase kinetic energy of a system?

Yes. It does contradicts our earlier knowledge that magnetic forces cannot do any work and hence cannot increase kinetic energy of a system.


But, our earlier knowledge about the above situation comes from the Lorentz equation, which is , we understood that the a “Uniform magnetic field” can not do any work on the charge,q.


But this equation would not apply when the magnetic field is non-uniform. In the given case, when two opposite poles are placed proximal, each of the magnets experiences a non-uniform magnetic field and there will be instantaneous magnetic moment and that will produce the movement.


To summarize, both the poles are in the influence of an external force, which is the cause for the kinetic energy dissipated, and it is not the internal magnetic force.


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