We know that reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. This “phantom power” is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. The mathematical symbol for reactive power is (unfortunately) the capital letter Q. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always).continue..

Vectors are simply another way to draw sine waves. You'll see its not difficult and actually makes things easier. Vectors, as used in this discussion, are representations of a sine wave of current relative to a sine wave of voltage. Instead of showing the current as a sine wave, the vector shows it as a straight line that points in a direction. The length of the line represents the RMS value of the current (remember, peak value x 0.707) and the direction of the line represents the phase angle of the current relative to the voltage (this is the "offset" as discussed in the "Power Factor" section).continue..

Select the calculation method from the drop-down menu and the required input values will be highlighted in orange. Add numbers to the highlighted fields and use the buttons to run the calculator for each of the five methods..continue..

Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt. Electric energy is transmitted with overhead lines on pylons like these in Brisbane, Australia.
For underground transmission see high voltage cables.When electric current flows in a circuit, it can transfer energy to do mechanical or thermodynamic work. Devices convert electrical energy into many useful forms, such as heat (electric heaters), light (light bulbs), motion (electric motors), sound (loudspeaker), information technological processes (computers), or even chemical changes. Electric Power can be produced mechanically by generation, or chemically, or by direct conversion from light in photovoltaic cells, also it can be stored chemically in batteries..continue..

Reactive power is a concept used by engineers to describe the background energy movement in an Alternating Current (AC) system arising from the production of electric and magnetic fields. These fields store energy which changes through each AC cycle. Devices which store energy by virtue of a magnetic field produced by a flow of current are said to absorb reactive power; those which store energy by virtue of electric fields are said to generate reactive power.continue..

•In alternating-current power transmission and distribution, the product of the rms voltage and amperage. Note 1: When the applied voltage and the current are in phase with one another, the apparent power is equal to the effective power, i.e., the real power delivered to or consumed by the load. If the current lags or leads the applied voltage, the apparent power is greater than the effective power. Note 2: Only effective power, i.e., the real power delivered to or consumed by the load, is expressed in watts. Apparent power is properly expressed only in volt-amperes, never watts. See diagram under effective power.continue..

The REACTIVE POWER is sometimes defined as the "phantom" power which has a unit of VAR or Volt-ampere reactive. Reactive power is represented by the letter Q.
The TRUE POWER (real power) on the other hand, is the one that utilizes the actual power and has a unit of watts. Another term for this is the useful power. So, as the word describes, it is the power that we use to operate devices and machineries. Also, True power is represented by the letter P.
The third component, which is the APPARENT POWER is the power required or drawn from the source. This is the combination of the reactive and true power and has a unit of VA or Volt-Ampere. Apparent Power can be computed by simply multiplying the circuit's voltage and current. Apparent Power is represented by the letter S.continue..

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