scenario: If any generator ultimately 'pushes' current (free surface electrons) down a wire, moving trillions of trillions of electrons through power wires towards our homes and other uses . . . what is the source of electrons at the generator site to replenish electrons? There can not be an endless supply, so where are they initially taken from, and how are electrons returned to this starting point of electrical generation (in this specific example or in general for non-cyclic systems).