Page 386 - Basic Electrical Engineering

Alternately

or,

or,

At resonance, frequency is f , current I = V/R, power factor is unity, voltage
0
0
drops across R, L, C are respectively, V , V , and V and supply voltage V
C
R
L
is equal to the voltage drop across the resistance V .
R
Since at resonance, current is maximum and is very high, power
2
dissipation I R is maximum and the rate of energy storage in the inductor
0
and the capacitor is maximum and they are equal. The value of R is usually

small (this is the resistance of the inductive coil), and hence voltage drop
across it, i.e., V is also small as compared to the voltage drops across L and
R
C. Voltage drops V and V are higher than V . However, as V = V and
L
R
C
L
C
they are in phase opposition as shown in Fig. 3.67 (b), the net voltage across
L and C in series, V is equal to zero. Thus, the supply voltage will be equal
X
to V .
R
Students will find it interesting to note that under the resonant condition
the voltage across C or L will be many times more than the supply voltage.
The power which is dissipated in the resistor is called active power. The

energy which is stored in the inductor and the capacitor are due to reactive
power. The energy stored in the inductor and the capacitor oscillates between