Exam Question

(a) True Power The actual amount of power being dissipated or performs the useful work in the circuit is called as active or true or real power. It is measured in watts, practically measured in KW(kilowatts) & MW(megawatts) in power systems. It is denoted by the letter P (capital) and it is equal to the average value of P = VI cos φ. It is the required outcome of an electrical system which drives the circuit or the load.
P = VI cos φ
Apparent Power The combination of true power & reactive power is called apparent power. Without reference to any phase angle, the product of voltage & current gives the apparent power. The apparent power is very useful for rating the power equipment. It can also be expressed as the square of the current multiplied by the circuit’s impedance. It is denoted by the letter S & measured in Volt-Amperes (VA), practical units include KVA (Kilo volt-amperes) & MVA (mega volt-amperes).
The power factor is the cosine angle between the voltage & current. The power factor can be expressed in terms of the above discussed power forms. Power factor defines the efficiency of the circuit.