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The volt-ampere (SI symbol: VA, [1] sometimes V⋅A or V A) is the unit of measurement for apparent power in an electrical circuit. It is the product of the root mean square voltage (in volts) and the root mean square current (in amperes). [2] Volt-amperes are usually used for analyzing alternating current (AC) circuits.
The difference in electric potential across two points along a conducting wire carrying one ampere of constant current when the power dissipated between the points equals one watt. [ 32 ] = 1 V = 1 W/A = 1 kg⋅m 2 /(A⋅s 3 ) = 1 J/C
They made the volt equal to 10 8 cgs units of voltage, the cgs system at the time being the customary system of units in science. They chose such a ratio because the cgs unit of voltage is inconveniently small and one volt in this definition is approximately the emf of a Daniell cell , the standard source of voltage in the telegraph systems of ...
Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to include replacement of a quantity with a corresponding quantity that describes the same physical property.
Electric power is the rate of transfer of electrical energy within a circuit.Its SI unit is the watt, the general unit of power, defined as one joule per second.Standard prefixes apply to watts as with other SI units: thousands, millions and billions of watts are called kilowatts, megawatts and gigawatts respectively.
The International System of Electrical and Magnetic Units is an obsolete system of units used for measuring electrical and magnetic quantities. It was proposed as a system of practical international units (e.g., the international ampere, the international ohm, the international volt) by unanimous recommendation at the International Electrical Congress (Chicago, 1893), discussed at other ...
One faraday equals 9.648 533 212... × 10 4 coulombs. [5] In terms of the Avogadro constant (N A), one coulomb is equal to approximately 1.036 × 10 −5 mol × N A elementary charges. Every farad of capacitance can hold one coulomb per volt across the capacitor. One ampere hour equals 3600 C, hence 1 mA⋅h = 3.6 C.
The base value should only be a magnitude, while the per-unit value is a phasor. The phase angles of complex power, voltage, current, impedance, etc., are not affected by the conversion to per unit values. The purpose of using a per-unit system is to simplify conversion between different transformers.