The electric field in a metal which causes the movement of electrons acts with the same force both on the electrons and on the ions of the metal's structure, but these forces act in opposite directions. The force acting on the electrons causes them to accelerate. Under the electric field's effect, the electrons acquire a certain momentum which they give up to the ions on impact. In this, the average force with which the electrons act upon the conductor when they collide with the ions of the metal's structure is exactly equal to the force with which the electric field acts directly upon the ions, but it is opposite to this force in direction. Therefore a metal conductor through which current is passing does not experience any mechanical forces in the electrons' direction of motion.