An electrolyte is poured into a tall cylindrical vessel of radius R. Inside the vessel, parallel to its axis, there is a cylindrical metal rod of radius r0, the surface of which is coated with insulating paint (figure). The distance between the axes of the rod and the vessel is equal to d. A current I, uniformly distributed over the cross section, flows parallel to the axis in the electrolyte and returns back along the rod. Find the force with which the magnetic field created by the currents under consideration acts per unit length of the rod. Where does this power go?

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