Hi all, if you wonder why domestic / AC mains equipment is also quoted as KVA, there is a reason. Many will know about how an electric motor works with a coil of wire moving in a magnetic field causes the build up of a magnetic field in the coil. Everything takes time to happen so it lags a bit.
Some of you will also know about capacitors charging up and of course discharging and they will be slow to discharge. So in one case the voltage is slow to build up in the coil of wire and the current is slow to discharge from a capacitor.
All circuits have a capacitive and an inductive (Inductance is the build up of the magnetic field in the coil of wire and also a measurement of an induced magnetic field) effect.
DC circuits are mainly resistive.
If you look at many of the 'works' of domestic machines (white goods) they come with a fair number of components. So the AC waveform has to be thought of as voltage going up and down at 50 cycles per sec (or Hertz), as well as current and they are more often than not out of phase.
So maximum current (A) multiplied by maximum volts (V) is given as VA the K just multiplies it up by a thousand.
Hope it helps although a bit off piste.