current
20.2 Ohms Law: Resistance and Simple Circuits What drives current? We can think of various devicessuch as batteries, generators, wall outlets, and so onwhich are necessary to maintain a current. All such devices create a potential difference and are loosely referred to as voltage sources. When a voltage source is connected to a conductor, it applies a potential difference V that creates an electric field. The electric field in turn exerts force on charges, causing current.