Electrical circuits lecture notes b. Tech

Superposition Theorem
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Reciprocity Theorem
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Tellegen’s Theorem
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Substitution Theorem
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Compensation Theorem
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Millman’s Theorem

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INTRODUCTION: 
Any complicated network i.e. several sources, multiple resistors are present if the 
single element response is desired then use the network theorems. Network theorems are also can 
be termed as network reduction techniques. Each and every theorem got its importance of 
solving network. Let us see some important theorems with DC and AC excitation with detailed 
procedures. 
Thevenin’s Theorem and Norton’s theorem (Introduction) : 
Thevenin’s Theorem and Norton’s theorem are two important theorems in solving 
Network problems having many active and passive elements. Using these theorems the networks 
can be reduced to simple equivalent circuits with one active source and one element. In circuit 
analysis many a times the current through a branch is required to be found when it’s value is 
changed with all other element values remaining same. In such cases finding out every time the 
branch current using the conventional mesh and node analysis methods is quite awkward and 
time consuming. But with the simple equivalent circuits (with one active source and one 
element) obtained using these two theorems the calculations become very simple. Thevenin’s 
and Norton’s theorems are dual theorems. 
Thevenin’s Theorem
Statement : 
Any linear, bilateral two terminal network consisting of sources and 
resistors(Impedance),can be replaced by an equivalent circuit consisting of a voltage source in 
series with a resistance (Impedance).The equivalent voltage source 
V
Th
is the open circuit 
voltage looking into the terminals(with concerned branch element removed) and the equivalent 
resistance