Electrical power is the rate per unit time at which the amount of electrical energy that is transformed to some other form of energy.Electrical Power is classified as Active Power, Reactive Power, and Apparent Power.
Electrical power is an important aspects of any electrical and electronics circuits. In this article, we will discuss all about Electrical power and its significance.
Electrical Power Definition:
In general science power is simply defined as the capacity to do work. In other words, it is defined as the rate of doing work.
Whereas In electrical engineering, Electrical power is the rate per unit time at which the amount of electrical energy is transformed into some other form of energy (such as heat, light, mechanical power, etc). Electrical power is one of the key concepts associated with Electrical Engineering.
Mathematically, Electrical power is defined as the product of voltage drop across the electrical element in the circuit and current flowing through it. It is measured in terms of Electrical Energy per unit time.
Unit of Electrical Power
When we talk about Electrical Power then it is considered as Active power consumed by the circuit element. So the unit of Electrical power (Active power) is Watt or joule per second.[ ##eye## Different Parts of transformer and their functions]
Watt is the SI unit of the power which is defined as the rate of conversion of 1-joule electrical energy per unit second.
Hence the Power
consumed in an electrical circuit is said to be 1 watt if one ampere current flows through the circuit when a potential difference of one volt maintains across it.
1 kW = 1000 Watt
Types of Electrical Power
- DC power
- AC power
1. DC Power
Power consumed in the DC circuit is known as DC power. It is produced by a fuel cell, batteries, DC generators, etc.
Mathematically DC power is defined as the product of voltage and current through the circuit.
So P = V * I
2. AC Power
The electrical power associated in AC circuit is known as Complex Power. Whereas Complex Power is the combined form of Active, Reactive, and Apparent Power in AC circuit. So AC power or complex power is further devided into three parts.
- Active Power
- Reactive Power
- Apparent Power
Active Power (kW)
In the case of DC circuit or in pure resistive AC circuit, active power is calculated as the product of voltage and current in the circuit. Whereas in the case of AC circuit it is calculated as:
Reactive Power (kVAR)
Reactive power is not a useful power for consumers so it is interpreted as wattless power. It represents an extra burden on the electricity supply system and on the consumer's bill also. Whereas this is required in the circuit to produce the electric and magnetic field for working of capacitors and inductors in the circuit. It has a direct impact on the power factor of the circuit. It only exists in electrical system when voltage and current in an AC circuits are not in phase.
[ ##eye## Power Factor Correction techniques]
This reactive power does not perform any useful work in the circuit. It is denoted by an English alphabet Q and measured in VAR, kVAR, or MVAR.
In the case of the DC circuits, there are no concepts of Reactive Power. Whereas for the AC circuit it is calculated as

Apparent Power (kVA):
Mathematically Apparent power is defined as the product of root mean square (RMS) value of voltage and current irrespective of its phase angle. It is denoted by an English alphabet 'S' and It is measured in kVA, MVA.
In the case of the DC circuit, it is the total power of the circuit. Whereas for the AC circuit it is calculated as :
Power Triangle
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