When the metal ball moves in the magnetic field, the free electrons are distributed over the surface of the ball due to the action of the Lorentz force so that the resultant electric field in the bulk of the ball is uniform and compensates the action of the magnetic field. After the equilibrium has been attained, the motion of electrons in the bulk of the metal ceases. Therefore, the electric field strength is
We arrive at the conclusion that the uniform electric field emerging in the bulk of the ball has the magnitude
The maximum potential difference Δφmax emerging between the points on the ball diameter parallel to the vector Eres is