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Definition of Power

Power is defined as the rate of doing work. It is calculated by the following formulas:

 1) P = V x I whereupon:

     P= power measured in watts

    V= voltage measured in volts

     I = current measured in amperes or amps

 2) It can also be expressed as P = I squared x R whereupon:

    P= power measured in watts

    I = current measured in amperes or amps and then squared

    R= Resistance in the circuit of interest

 3)  It can also be expressed as P = V squared divided by R whereupon:

      P= power measured in watts

     V = voltage measured in volts and then squared

     R= Resistance in the circuit of interest

 It should be noted that formulas 2 and 3 are derived from formula 1 by algebraic solution.

A volt-ampere (VA) is the unit used for the apparent power in an electric circuit, equal to the product of root-mean-square (RMS) voltage and RMS current. In direct current (DC) circuits, this product is equal to the real power (active power) in watts. Volt-amperes are useful only in the context of alternating current (AC) circuits (sinusoidal voltages and currents).

If you wish to acquire a better understanding of Electronics Theory, I suggest you go to  the following  link: Electronics

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