# Difference between real and reactive power

Real power is the energy dissipated by the resistor in one second. Joules per second.

What is reactive power then?

Is it the energy being stored in inductor and capacitor in one second?

If we then connect inductor and capacitor having stored energy with a resistor, then would the rate of energy dissipation by resistor and the rate of energy supplied by inductor or capacitor be the same?

• Reactive power is where the current waveform is out of phase with the voltage waveform. This can cause issues where the current is high, but the voltage is low, so in terms of Watts, very little work is being done. Nov 26 '21 at 10:15
• Does this answer your question? What is reactive Power and how it is generated and what is its source? Nov 26 '21 at 11:49
• Big picture is: reactive power/current is extra current that has to flow in your AC circuit to charge and discharge inductors and capacitors. They "take" extra current from the source and "give it back" later on in the cycle. Although this power isn't consumed or used, the whole system - source, load, and connecting lines - need to be sized to deal with it.
– vir
Nov 26 '21 at 18:51

What is reactive power then?

It is a power travelling back and forth from the source to the load.

Is it the energy being stored in inductor and capacitor in one second?

$$P=\dfrac{dE}{dt}$$

If we talk about the power, then it is not. But there is a relation between power and energy, not necessarily it has to be 1 second period.

If we then connect inductor and capacitor having stored energy with a resistor, then would the rate of energy dissipation by resistor and the rate of energy supplied by inductor or capacitor be the same?

Of course, if the source is turned off = short circuit, the energy from inductor or capacitor will be dumped in the resistor.

• If 1 joule of energy is stored in 1 second in an inductor or capacitor, then won't we call it 1 kvar of reactive power?
– Alex
Nov 26 '21 at 15:13
• @Alex 1VA = 1 J/s Nov 26 '21 at 16:33
• Yah sorry VAR not Kvar. Then my statement is right if I place KVAR with VAR?
– Alex
Nov 26 '21 at 16:38

Reactive power is what is loading your supply lines without producing results. Apparent power is RMS voltage times RMS current while actual power transfered is the time average of the instantaneous product of voltage times current. The difference is reactive power. It heats the wires and trips fuses but ends up (minus transport losses) where it started.

What to call the power balance in an RLC combination depends on just where you draw or rather cut the line to measure power transfer.