Page 305 - Basic Electrical Engineering

in the magnetic field. As the current starts reducing, the magnetic field
collapses and the energy is returned to the supply source. Thus, in one half
cycle power is drawn by the inductor and in the next half cycle power is

returned to the source. This way the net power absorbed by the inductor
becomes zero. The power which is being circulated from the source to the

inductor and back to the source is called reactive power which will also be
discussed in a separate section.

AC applied across a pure capacitor

A sinusoidal voltage source has been shown connected across a pure
capacitor in Fig. 3.16 (a). When current starts flowing, the capacitor starts

getting charged. The charge, q of the capacitor in terms of capacitance of the
capacitor, C and supply voltage, v is expressed as

q = Cv

Current, i is the rate of flow of charge. Therefore,

= ωC V cos ωt
m

or,