---
title: "Norton theorem steps and comparison"
subject: "Basic Electrical Engineering"
chapter: 3
key: "semester_1/basic_electrical_engineering:norton-theorem-steps-compare-thevenin"
source: https://www.bctengineer.com/q/semester_1/basic_electrical_engineering/norton-theorem-steps-compare-thevenin
site: BCT Engineering
---

# Norton theorem steps and comparison

Basic Electrical Engineering · Chapter 3: Network Theorems

- Asked in: 2068 Chaitra, 6 marks
- Video: [Norton's Theorem and Thevenin's Theorem - Electrical Circuit Analysis](https://www.youtube.com/watch?v=-kkvqr1wSwA) — The Organic Chemistry Tutor
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_1/basic_electrical_engineering/norton-theorem-steps-compare-thevenin
- Whole chapter: https://www.bctengineer.com/md/semester_1/basic_electrical_engineering/chapter-3

## Question

State Norton's description theorem and list the steps for Nortonizing a circuit. Compare the Norton's equivalent circuit to the Thevenin's equivalent circuit.

## Short answer

Norton’s theorem: any linear two-terminal network can be replaced by a current source IN (short-circuit current) in parallel with RN (resistance seen from terminals with sources zeroed). Compared to Thevenin: Norton uses a current source in parallel, Thevenin a voltage source in series; RN = Rth; conversion by IN = Vth/Rth.

## Answer

#### Norton's theorem
Any linear two-terminal network containing sources and resistors can be replaced, as seen from its terminals, by a **current source I_N in parallel with a resistance R_N**. I_N is the short-circuit current between the terminals and R_N is the resistance seen from the terminals with all independent sources set to zero.

#### Steps for Nortonizing a circuit
1. Remove the load and mark the terminals a and b.
2. Short a-b and calculate the short-circuit current I_N.
3. Set all independent sources to zero (voltage sources shorted, current sources opened) and find R_N between a and b.
4. Draw I_N in parallel with R_N and reconnect the load: I_L = I_N × R_N/(R_N + R_L).

```text
 Norton equivalent
 o----+--------+------o a
     (I_N)   [R_N]   [R_L]
 o----+--------+------o b
```

#### Norton equivalent versus Thevenin equivalent
| Point | Norton | Thevenin |
|---|---|---|
| Source | current source I_N | voltage source V_th |
| Resistance | R_N in parallel | R_th in series |
| Key quantity | short-circuit current | open-circuit voltage |
| Resistance value | R_N = R_th | R_th |
| Conversion | I_N = V_th/R_th | V_th = I_N R_N |
| Load current | I_L = I_N R_N/(R_N + R_L) | I_L = V_th/(R_th + R_L) |
| Convenient for | parallel networks (nodal analysis) | series networks (mesh analysis) |

They are equivalent at the load terminals (source transformation), but not inside: with an open load, the Norton circuit dissipates power in R_N while the Thevenin circuit does not.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does Norton's theorem say a linear two-terminal network can be replaced by?
   A. A current source I_N in parallel with R_N
   B. A current source in series with R_N
   C. A voltage source in series with R_N
   D. A resistor R_N alone
   Answer: A. I_N is the short-circuit current and R_N the resistance with sources set to zero. (Key point: Norton's theorem)

2. Which is the correct order of steps for Nortonizing?
   A. Short the load, add all resistances, divide by the voltage
   B. Zero all sources first, then measure I_N
   C. Open terminals for V_oc, then compute R_N, then add a series source
   D. Remove load, short terminals for I_N, zero sources for R_N, draw I_N parallel R_N and reconnect load
   Answer: D. Remove the load, find I_N by shorting a-b, find R_N with sources zeroed, then redraw and reconnect the load. (Key point: Steps)

3. Which formula gives the load current from the Norton circuit?
   A. I_L = I_N (R_N + R_L)/R_N
   B. I_L = I_N/(R_N R_L)
   C. I_L = I_N R_N/(R_N + R_L)
   D. I_L = I_N R_L/(R_N + R_L)
   Answer: C. Current divides between R_N and R_L; the load gets I_N x R_N/(R_N + R_L). (Key point: Load current)

4. How do the equivalents differ internally despite being identical at the load terminals?
   A. Norton gives different load current
   B. Thevenin always has a higher R
   C. With open load, Norton dissipates power in R_N but Thevenin dissipates none
   D. They differ in R value
   Answer: C. They are equivalent only at the terminals; internally the open-circuit Norton circuit still circulates I_N through R_N. (Key point: Internal difference)

## Related in Basic Electrical Engineering

- [Thevenin and Norton duality](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_engineering%3Athevenin-norton-dual) — Basic Electrical Engineering, chapter 3
- [Steps to find Norton resistance](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_engineering%3Anorton-equivalent-resistance-steps) — Basic Electrical Engineering, chapter 3
- [Power in 3Ω using Norton theorem (10 V, 10 A)](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_engineering%3Anorton-power-3-ohm-10v-10a-1-ohm) — Basic Electrical Engineering, chapter 3
- [Power in 5Ω using Norton theorem (2 A, 10 V)](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_engineering%3Anorton-power-5-ohm-2a-10v) — Basic Electrical Engineering, chapter 3
- [Thevenin theorem, current in 10Ω](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_engineering%3Athevenin-current-10-ohm-20v-12v) — Basic Electrical Engineering, chapter 3
- [Thevenin theorem, current in 13Ω](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_engineering%3Athevenin-13-ohm-200v-50v-180v) — Basic Electrical Engineering, chapter 3

## Related in other subjects

- [Thevenin's theorem and steps](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Athevenin-steps) — Basic Electronics Engineering, chapter 1
- [Thevenin theorem for antennas](https://www.bctengineer.com/question.md?key=semester_6%2Fpropagation_and_antenna%3Athevenin-theorem) — Propagation and Antenna, chapter 1
- [Thevenin: 90, 50, 130 ohm circuit](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Athevenin-90-50-130) — Basic Electronics Engineering, chapter 1, asked 3×
- [Thevenin: 100, 60, 150 ohm circuit](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Athevenin-100-60-150) — Basic Electronics Engineering, chapter 1, asked 2×