We can take Impedance triangle idea one step further by converting the impedance triangle into a power triangle representing the three elements of power in an AC circuit.
Ohms Law tells us that in a DC circuit, power (P), in watts, is equal to the current squared times the resistance.
So, we can multiply the three sides of our impedance triangle above by square of current to obtain the corresponding power triangle as shown below.
Real Power=P=I² R Watts,(W)
Reactive Power Q=I² X Volt Ampere Reactive(VAR)
Apparent Power S=I² Z Volt Ampere (VA)
Z=R+jX and S=P+jQ
AC apparent Power is a complex quantity made up of Real Active Power & Imaginary Reactive Power.
It is the real resistance that leads to the dissipation of real active power.
It is the imaginary reactance that leads to the reactive power.
The sum of the real power and the reactive power yields the apparent power.

Real Power in AC Circuits:

Real power (P), also known as true or active power, performs the real work within an electrical circuit.
Real power, measured in watts, defines the power consumed by the resistive part of a circuit.
As resistances do not produce any phasor difference (phase shift) between voltage and current waveforms, all the useful power is delivered directly to the resistance and converted to heat, light and work.
The power consumed by a resistance is real power which is fundamentally the circuits average power.
P=VI cos φ, Where V & I are RMS values of Voltage & current
φ is the Power Factor angle, i.e. the angle between V & I

Reactive Power in AC Circuits:

Reactive power (Q), (sometimes called wattless power) is the power consumed in an AC circuit that does not perform any useful work.
But it has a big effect on the phase shift between the voltage and current waveforms.
Reactive power is linked to the reactance produced by inductors and capacitors and counteracts the effects of real power.
Reactive power does not exist in DC circuits.
Q=VI sin φ, Where V & I are RMS values of Voltage & current
φ is the Power Factor angle, i.e. the angle between V & I

The product of the rms voltage, V applied to an AC circuit and the rms current, I flowing into that circuit is called the volt-ampere product (VA) given the symbol S and whose magnitude is known generally as apparent power.
As apparent power is made up of two parts, the resistive power which is the in phase power or real power in watts and the reactive power which is the out of phase power in volt amperes(VA).
We can show the vector addition of these two power components in the form of a power triangle.
A power triangle has four parts: P, Q, S and power factor angle or phase angle.