Best Tutorial on Active Power, Reactive Power & Apparent Power.

In this tutorial, we are going to learn about Active Power, Reactive Power & Apparent Power.

It can be defined as the rate at which energy conversion takes place in one form to other per unit time.

Alternating current can be of two types positive or negative.

  • Active Power (+)
  • Reactive Power (-)
  • Apparent Power

Positive Power – Source to Load

Negative Power – Load to Source

  • Active Power – Nature of active power is positive. It means always flow source to load.

Completely utilize by load, there is no loss in transmission. It is denoted by P and unit is watt (W).

Here below is a circuit taking for example for active power.


I=230/80 = 2.87A

P = I2 X R

P = (2.87)2 X 80

P = 658.95W

  • Reactive Power – Nature of reactive power is negative. It means always flow load to source. It is never utilize by load. It does not have any useful work in transmission line just move back and forth between sources to load. Net power consume in pure inductive or pure capacitive load is zero, it is denoted Q and unit is VAR.

For reactive power we are taking example of below circuit which is the formula:

XL = 2∏FL

=2 X 3.14 X 50 X 0.2 ( F =50Hz, 1Henry = .001)

= 62.8 OHM

V = IR , I = 230/62.8 = 3.66A

Apparent Power – It is defined as total power transfer to load and load is a combination of the resistive, capacitive and inductive components. All load consume power are a combination of resistor, capacitor and inductor which are the power of Motor, TV, Fridge and Fan AC.

Apparent Power denoted by S and unit is VA.

S2 = P2 + Q2

Apparent Power = Active Power + Reactive Power.

Here below is the circuit taking an example for apparent power.

Power = I2 X R

Z = √R2 + XL2

Z = √802 + (62.8)2

Z = 101.70 OHM

I = 230 / 101.70 = 2.26A

Now we can see all the power calculation formulas for power.

Apparent Power = I2 X Z = (2.26A)2 X (101.70) = 519.44 VA

Active Power = I2 X R = (2.26A)2 X (80) = 408.608 Watt

Reactive Power = I2 X XL = (2.26A)2 X (62.8) = 320.75 VAR

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