Review and expand on voltage difference, volts and electrical energy. Discuss resistance to flow of electrons and compare to resistance to flow of water through different circumference pipes. The unit of measurement of resistance is the Ohm. Discuss current flow as the number of electrons passing a given point on a conductor in one second. Compare current flow of electricity to the flow of water in a stream or through pipes. Indicate the factors which will influence flow and resistance. The flow of current is measured in amps.