Electrical Definitions


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Electrical Definitions

Letter - V


Provided with a means to permit circulation of air sufficient to remove an excess of heat, fumes, or vapors.


Volatile Flammable Liquid

A flammable liquid having a flash point below 38C (100F), or a flammable liquid whose temperature is above its flash point, or a Class II combustible liquid that has a vapor pressure not exceeding 276 kPa (40 psia) at 38C (100F) and whose temperature is above its flash point.



The unit of voltage or potential difference. The unit of electromotive force, electrical pressure, or difference of potential. Represented by E or V.


Volt Amperes

The product of the voltage across a circuit and the current in the circuit. Expressed in VA.



Electrical pressure, the force which causes current to flow through a conductor.


Voltage (of a circuit)

The greatest root-mean-square (rms) (effective) difference of potential between any two conductors of the circuit concerned.


Voltage Drop

The loss of voltage between the input to a device and the output from a device due to the internal impedance or resistance of the device. In all electrical systems, the conductors should be sized so that the voltage drop never exceeds 3% for power, heating, and lighting loads or combinations of these. Furthermore, the maximum total voltage drop for conductors for feeders and branch circuits combined should never exceed 5%.


Voltage to Ground

For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit.


Voltage, Nominal

A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts). The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment.


Voltage Ratio

The voltage ratio of a transformer is the ratio of the r.m.s. primary terminal voltage to the r.m.s. secondary cur-rent, under specified conditions of load.