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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.
At that time, the volt was defined as the potential difference [i.e., what is nowadays called the "voltage (difference)"] across a conductor when a current of one ampere dissipates one watt of power. The "international volt" was defined in 1893 as 1 ⁄ 1.434 of the emf of a Clark cell.
The conductors between a voltage source and a load are called lines, and the voltage between any two lines is called line voltage. The voltage measured between any line and neutral is called phase voltage. [4] For example, in countries with nominal 230 V power, the line voltage is 400 V and the phase voltage is 230 V.
Since power is defined as the product of current and voltage, the ampere can alternatively be expressed in terms of the other units using the relationship I = P/V, and thus 1 A = 1 W/V. Current can be measured by a multimeter, a device that can measure electrical voltage, current, and resistance.
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension is the difference in electric potential between two points. [1] [2] In a static electric field, it corresponds to the work needed per unit of charge to move a positive test charge from the first point to the second point.
An op amp without negative feedback (a comparator) The amplifier's differential inputs consist of a non-inverting input (+) with voltage V + and an inverting input (−) with voltage V −; ideally the op amp amplifies only the difference in voltage between the two, which is called the differential input voltage.
Ampacity is a portmanteau for ampere capacity, defined by United States National Electrical Codes.Ampacity is defined as the maximum current, in amperes, that a ...
Voltage: The amp's power supply voltage limits the maximum amplitude of the waveform it can output. This determines the peak momentary output power for a given load resistance. [1] [2] Current: The amp's output devices (transistors or tubes) have a current limit, above which they are damaged.