Bài giảng Electrical and electronic principles - Week 2

TRƯỜNG ĐẠI HỌC SƯ PHẠM KỸ THUẬT 
TP. HỒ CHÍ MINH 
ELECTRICAL AND ELECTRONIC 
PRINCIPLES 
WEEK 2 
Cuong Q. Ngo 
Last classes 
• Branch; node; loop 
• KCL 
• KVL 
2 
CONTENTS (Today) 
• Methods of analysis 
• Thevenin’s theorem 
• Norton theorem 
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Methods of analysis 
• Mesh analysis 
• Nodal analysis 
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1.1 Mesh analysis 
• A mesh is a loop which does not contain any other loops 
within it. 
• Paths abefa and bcdeb are meshes, but path abcdefa is not 
a mesh. 
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1.1 Mesh analysis 
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1.1 Mesh analysis 
• Find the branch currents and using mesh analysis 
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1.1 Mesh analysis 
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1.1 Mesh analysis 
• Use mesh analysis to find the current in the circuit below 
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1.1 Mesh analysis 
• Solution 
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1.1 Mesh analysis 
• Mesh Analysis with Current Sources 
– Case 1: When a current source exists only in one mesh 
• In the above circuit, we set i2 = - 5 A 
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1.1 Mesh analysis 
• Mesh Analysis with Current Sources 
– Case 2: When a current source exists between two 
meshes 
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1.2 Nodal analysis 
• Nodal analysis provides a general procedure for analyzing 
circuits using node voltages as the circuit variables. 
• 
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1.2 Nodal analysis 
• Calculate the node voltages (1; 2) in the circuit below 
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1.2 Nodal analysis 
• At node 1 
• At node 2 
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2.1 Thevenin’s theorem 
• Finding Vth and Rth 
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2.1 Thevenin’s theorem 
• If the network has dependent source 
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2.1 Thevenin’s theorem 
• Find the Thevenin equivalent circuit of the circuit to the left of 
terminal a-b 
• Then find the current through RL = 6, 16 Ω 
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• Answer 
 Rth = 4; Vth = 30 
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2.1 Thevenin’s theorem 
• Problem 1 
• Using Thevenin’s theorem, find the equivalent circuit to the 
left of the terminals a-b in the circuit below. Then find I. 
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• Answer 
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2.1 Thevenin’s theorem 
• Problem 2* 
• Find the Thevenin equivalent of the circuit at the terminals: a-
b 
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• Answer 
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Norton’s theorem 
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Norton’s theorem 
• Finding Norton current 
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Norton’s theorem 
• Problem 5 
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Norton’s theorem 
• Answer 
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Norton’s theorem 
• Exercise: Solve the problem 5 by using Thevenin’s theorem 
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Norton’s theorem 
• Problem 6 
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Norton’s theorem 
• Answer 
30