Bài giảng Electrical and electronic principles: Chương 2 - ThS. Ngô Quốc Cường

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: ab

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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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