The electrical power (P) is a measure of the energy that results from the voltage (U) and the current (I). The dimension for the electrical power is the Watt (W), which is named after the inventor of the steam engine James Watt (1736 to 1818).
There is a direct relationship between power, voltage and current. The power increases proportionally with the voltage and the current.
One watt corresponds to a voltage of 1 V multiplied by a current of 1 A. This is true if the current is direct current or direct voltage.
If the power is dependent on an alternating voltage and falls at an ohmic resistor, then it is the actually converted power, the active power. To determine it, the effective values of current and voltage are multiplied together. Active power is expressed in watts (W).
If the load is an impedance, then it is an apparent power (S) and if it is a pure reactance, then it is a reactive power (Q). Apparent power is specified in volt-amperes( VA) and reactive power is specified in voltage-amperes reactive in( Var) to distinguish it. The different power specifications are related to each other the power factor.