Objects become charged because electrons are transferred between them. Electric current is the flow of electrons. Electric charge is not created or destroyed, it is merely moved around. Analogies between gravitational and electrical systems help us to understand abstract concepts like electric potential, which is also called voltage. Ohm’s Law is the basis of our understanding of electric circuits made of resistors because we can reduce combinations of resistors to one equivalent resistance. By understanding the relationships of resistances, currents, and voltages in series and parallel you can solve many circuit problems.