Page 298 - Basic Electrical Engineering

with one inductance and one capacitance in parallel. Accordingly circuits are
named as L-R circuits, L-R-C circuits, etc. We will take up few series
circuits, few parallel circuits, and some series–parallel circuits and calculate

the main current, branch currents, power, power factor, etc. Before this, we
will discuss the behaviour of R, L, and C in ac circuits

3.2.1 Behaviour of R, L, and C in AC Circuits

In this section we will study the relationship of applied voltage and current in
an ac circuit involving only a resistance, an inductance, and a capacitance.

When a resistance is connected across an ac supply we call it a purely
resistive circuit. Similarly an inductance coil connected across an ac supply is

called a purely inductive circuit and a capacitance connected across an ac
supply is called a purely capacitive circuit. We shall study the phase

relationship between the applied voltage and current flowing in each case
under steady-state condition.

AC applied across a pure resistor

When we say a pure resistance we assume that the resistance wire does not
have any inductance or capacitance. Fig. 3.13 shows a pure resistance
connected across an ac supply. The voltage and current wave forms as well as

the phasor diagram showing the positions of voltage and current have been
shown. The instantaneous value of

Voltage, v of the source is v = V Sin ω t
m
Where, V is the maximum value of the voltage in Volts; ω = 2πf rad/sec;
m
and f is the frequency of supply voltage in cycles per second.

The current flowing though the circuit will be

At