Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Objectives:
• Describe Kirchhoff's voltage and current laws.
• Reduce a circuit to a single Thevenin equivalent circuit.
• Reduce a circuit to a single Norton equivalent circuit.
• Solve a circuit using the superposition theorem.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Kirchhoff’s Laws
1. The algebraic sum of the voltage sources and voltage drops in a closed circuit must equal zero.
2. The algebraic sum of the current entering and leaving a point must equal zero.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Kirchhoff’s Current Law
“The algebraic sum of the current entering and leaving a point must equal zero.”
This law is for parallel circuits and states that the total current is the sum of all of the branch currents.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Kirchhoff’s Current Law
The algebraic sum of the currents entering and leaving a point must equal zero

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Kirchhoff’s Voltage Law
“The algebraic sum of the voltage sources and voltage drops in a closed circuit must equal zero.”
This law states that the sum of the voltage drops in a series circuit must equal the applied voltage.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Kirchhoff’s Voltage Law
“The algebraic sum of the voltage sources and voltage drops in a closed circuit must equal zero.”
This law states that the sum of the voltage drops in a series circuit must equal the applied voltage.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Kirchhoff’s Voltage Law
The algebraic sum of the voltages around any closed loop must equal zero
.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Thevenin’s Theorem
Thevenin’s theorem simplifies a circuit into an equivalent circuit which contains a single voltage source and series resister.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Thevenin’s Theorem
The equivalent Thevenin Circuit consists of a single power source and single series resistor.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Norton’s Theorem
Norton’s Theorem is used to reduce a circuit network into a simple current source and a single parallel resistance.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Norton’s Theorem

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and
Superposition Theorems
Superposition Theorem
Any branch of a circuit supplied by a multipower source can be determined by finding the current produced in that particular branch by each of the individual power sources acting alone. All other power sources must be replaced by a resistance equivalent to their internal resistances. The total current flow through the branch is the algebraic sum of the individual currents produced by each of the power sources.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Superposition Theorem

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Review:
1. Kirchhoff's Laws can be used to solve unknown values for circuits that contain more than one power source.
2.
Thevenin’s theorem involves reducing a circuit network to a simple voltage source and series resistance.

Unit 9
Kirchhoff's Law, Thevenin’s, Norton’s, and Superposition Theorems
Review:
3.
Norton’s theorem involves reducing a circuit network to a current source and parallel resistance.
4. The superposition theorem is used to find the current flow through any branch of a circuit containing more than one power source.