Alternating current: Electric current that repeatedly reverses direction, twice each cycle. Usually at 60 cycles per second, or hertz. In North America, or 50 hertz elsewhere.
Ampere: SI unit of electric current. A flow of one coulomb of charge per second is one ampere.
Diode: An electric device that restricts current to flow in a single direction in an electric circuit.
Direct current: Electric current whose flow of charge is always in one direction.
Electric current: The flow of electric charge, measured in amperes.
Electric power: The rate at which electrical energy is converted into another form, such as light, heat or mechanical energy.
Electric resistance: The resistance of a material to the flow of electric current through it; measure in ohms.
Ohm: T he SI unit of electric resistance. one ohm is the resistance of a device that draws a current of one ampere where a voltage of one volt is impressed across it.
Ohm's law: The statement that the current in a circuit is directly proportional to the voltage impressed across the circuit, and is inversely proportional to the resistance of the circuit.
Potential difference: The difference in electric potential between two points.
Voltage source: A device, such as a dry cell or generator, that provides a potential difference.