Learning Objectives:

1. Understand the importance of Thevenin’s theorem.
2. Draw Complex Network into a Thevenin’s equivalent circuit.

It is possible to reduce a complex circuit to a single voltage source and series resistance connected to a load.

1. Find the load resistor.
2. Remove the Load Resistance R$_L$.
3. Calculate/measure the open circuit Thevenin’s voltage V$_{TH}$ across two open ends.
4. Replace all active sources with their internal resistance.
5. Calculate /measure the equivalent Thevenin’s Resistance R Across two open ends.
6. Now, Draw the equivalent circuit for given network. This is the Equivalent Thevenin’s Circuit.

Solved Example: 9155-01

Thevenin's theorem states that a given electrical network connected to a pair of terminals can be replaced with: (ISRO (VSSC) Tech Asst Electronics 2019)

A. A single voltage source in parallel with a single resistance

B. A single voltage source in series with a single resistance

C. A single current source in parallel with a single resistance

D. A single current source in series with single resistance

Correct Answer: B

Learning Objectives:

1. Explain Norton’s Theorem.
2. Outline the procedure adopted when using Norton’s Theorem.
3. Determine the short circuit current ISC and the equivalent Resistance RN (parallel)
4. Construct circuit base on Norton’s Theorem.
5. Solve linear circuits problem using Norton’s Theorem.

It is possible to reduce a complex circuit to a single current source and parallel resistance connected to a load.

1. Remove the load resistor RL or component concerned and short circuit the terminals. Find IN on the output terminals A and B.
2. Short-circuit the two voltage sources and open circuit terminals A and B, the two resistors are now connected together in parallel. Find RN.
3. Having found both the short circuit current, IN and equivalent internal resistance, RN. Draw the Nortons equivalent.
4. Replace the original load resistor (remove resistor) connected across terminals A and B and calculate current, I.

Solved Example: 9154-01

A two terminal network is connected to a resistive load whose resistance is equal to Norton resistance of the network. What will be the load current if Norton current is I$_n$? (DSSSB JE EE Nov 2019)

A. $\dfrac{2I_n}{3}$

B. $\dfrac{I_n}{2}$

C. $2I_n$

D. $I_n$

Correct Answer: B

Solved Example: 9154-02

When a circuit is represented by equivalent Thevenin's circuit and Norton's circuit: (MPSC Assistant Engineer EE Mains 2019 - Paper I)

A. Norton resistance < Thevenin resistance

B. Norton resistance = Thevenin resistance

C. Norton resistance > Thevenin resistance

D. Cannot comment

Correct Answer: B

Solved Example: 9154-03

Which of the following statements is true for Norton's Theorem? (DFCCIL Executive Electrical Sept 2021)

A. It is used to represent a linear network by an equivalent circuit having a current source and impedance in series with it.

B. It is used to represent a linear network by an equivalent circuit having a voltage source and impedance in series with it.

C. It is used to represent a linear network by an equivalent circuit having a voltage source and impedance in parallel with it.

D. It is used to represent a linear network by an equivalent circuit having a current source and impedance in parallel with it.

Correct Answer: D

Solved Example: 9154-04

Norton Theorem states that an entire network connected to a pair of terminals can be replaced with: (URSC (ISRO) Tech Asst (Electronics): August 2017)

A. A single voltage source in parallel with single resistance

B. A single current source in parallel with a single resistance

C. A single voltage source in series with a single resistance

D. A single current source in series with a single resistance

Correct Answer: B