Module 1: DC Circuits
Basic Electrical Engineering
Jayanta Bhusan Basu
DC Network Theorems
Apart from the various methods discussed so far, some very useful theorems are frequently applied for
analyzing the dc networks. Some of them are discussed below.
Superposition Theorem
This theorem is applicable to linear networks only; i.e. the effect produced within the network is directly
proportional to the responsible. If in a network there are more than one source acting together, then the
combined effect produced in the network can be calculated by summing (superimposing) the effect of each
source separately.
Statement of the theorem is as follows
In any linear active bilateral network constituting of more than one source the current flowing through any
branch is the sum of all the currents that will flow if each source is considered individually and all other
sources are replaced by their internal resistances.
Procedure: Consider for an electrical network having several independent energy sources are present, so
to find the current through a particular branch or voltage across that branch, following steps are used:
Step 1: Consider one source at a time and eliminate other sources from the circuit (voltage and
current sources are replaced by their respective internal resistances respectively)
Step 2: Calculate the current through or voltage across the particular element.
Step 3: Repeat the same procedure for all the other energy sources.
Step 4: Take the algebraic sum of individual effects produced by individual sources to obtain the
total current in or voltage across the element.
Example :
For the circuit determine the current through the 2 ohm resistance using Superposition Theorem.
