Page 29 - Basics of Electrical, Electronic and Communication

86 Chapter 4. Single Phase AC Circuits

discussed the sections 4.8 through 4.12, frequency of power waveform
is double of that of voltage and current waveforms.

p
v
i

t

φ

Figure 4.24: Voltage, current and power waveforms in RC circuit

i.e., Average power, P = V R I where V R = V cosφ from voltage

triangle shown in 4.23(b).
Therefore, P = V cos φ × I = V Icos φ

where V and I are rms values of voltage and current.
R
The term cos φ is called power factor of the circuit and cos φ =
Z
(From impedance triangle shown in Figure 4.20(b))

4.13 AC through series R-L-C circuit

Consider an ac circuit in which a resistor of resistance R Ω, an in-
ductor of inductance L Henry and a capacitor of capacitance C Farads
connected in series across an ac supply of V volts as shown in Figure
4.25.
Let V = rms value of applied voltage

I = rms value of resultant current

86