Discuss and use examples to define that the net charge in a current wire is zero. Define that the net charge of zero depends on electrons moving out of the circuit due to an electron pump replacing them as they move out. The pump is a voltage source, a battery or generator. Discuss that the potential difference caused by a batteries terminals is due to the difference in electrical potential energy/coulomb. Discuss the voltage difference due to outlet terminals. Introduce resistance, define the term and determine what factors cause the flow of current.