Electrical circuits lecture notes b. Tech

Series RLC Circuit Example 
A series RLC circuit containing a resistance of 12Ω, an inductance of 0.15H and a capacitor 
of 100uF are connected in series across a 100V, 50Hz supply. Calculate the total circuit 
impedance, the circuits current, power factor and draw the voltage phasor diagram
 
Inductive Reactance, X
L
. 
Capacitive Reactance, X
C
. 

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Circuit Impedance, Z 
Circuits Current, I. 
Voltages across the Series RLC Circuit, V
R
, V
L
, V
C
. 
Circuits Power factor and Phase Angle, θ. 
Phasor Diagram. 

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Concept of Reactance, Impedance, Susceptance and Admittance: 
Reactance
is essentially inertia against the motion of electrons. It is present anywhere 
electric or magnetic fields are developed in proportion to applied voltage or current, 
respectively; but most notably in capacitors and inductors. When alternating current goes 
through a pure reactance, a voltage drop is produced that is 90
o
out of phase with the current. 
Reactance is mathematically symbolized by the letter “X” and is measured in the unit of 
ohms (Ω).
 
Impedance
is a comprehensive expression of any and all forms of opposition to electron 
flow, including both resistance and reactance. It is present in all circuits, and in all 
components. When alternating current goes through an impedance, a voltage drop is 
produced that is somewhere between 0
o
and 90
o
out of phase with the current. Impedance is 
mathematically symbolized by the letter “Z” and is measured in the unit of ohms (Ω), in 
complex form 
Admittance
is also a complex number as impedance which is having a real part, 
Conductance (G) and imaginary part, Susceptance (B). 
(it is negative for capacitive susceptance and positive for inductive susceptance)