The nomenclature, volt (E), ampere (I) and ohm (R) with which electric energy is defined and measured.
Volt (E). The electrical pressure (electromotive force) which causes electricity to flow through a conductor is measured in volts. A volt is the unit of electrical pressure required to cause a current of one ampere to flow through a conductor having a resistance of one ohm. Voltage is also referred to as potential difference.
Ampere (I). The unit of electric current which will flow through a conductor with a resistance of one ohm under a pressure of one volt is one ampere. The ampere expresses the amount of current which flows through a conductor.
Ohm (R). The unit of resistance of a circuit through which a potential difference of one volt produces a current of one ampere. The ohm is usually defined as the resistance of a given conductor of a certain material, size and form.
The relationship between volts, amperes, and ohms is expressed in Ohm’s law as follows: I equals E/R, or E equals I x R, or R equals E/I. When I equals the current in amperes, E equals the electromotive force or pressure in volts, and R equals the resistance in ohms.