Norton resistance is found by?

Question

Examoogle · Accepted Answer

Shorting all voltage sources and opening all current sources

Explanation: Norton resistance ($R_N$) is the equivalent resistance of a linear, bilateral network as viewed from a specific pair of terminals. It is calculated by replacing all independent sources with their internal resistances, which implies short-circuiting independent voltage sources and open-circuiting independent current sources.

Working Principle: The principle relies on the property of 'deactivating' independent sources to isolate the passive network components. A voltage source has zero internal resistance, hence shorting it makes the potential difference across it zero. An ideal current source has infinite internal resistance, hence opening it makes the current through it zero. Once sources are deactivated, the equivalent resistance is determined using series and parallel circuit reduction techniques.

Key Formulas: $R_N = \frac{V_{th}}{I_{sc}}$ — Relationship between Norton resistance, Thevenin voltage, and Norton current; $R_{eq} = R_1 || R_2$ — Common calculation step for parallel branches

Key Points: Norton resistance is equal to Thevenin resistance ($R_N = R_{th}$).; Independent sources are 'killed' or deactivated to find the passive equivalent impedance.; Dependent sources must be left active and handled using an external test source ($V_{test}/I_{test}$) method.; The circuit is viewed from the open-circuited load terminals.

Advantages: Simplifies complex networks into a single current source and parallel resistor.; Efficient for analyzing circuits with parallel loads.

Disadvantages: Not ideal for networks with many series-connected components compared to Thevenin's theorem.; Requires careful handling of dependent sources.

Applications: Power system fault analysis.; Circuit simplification for electronic load impedance matching.; Analysis of transistor biasing circuits.

Additional Info: The process of shorting voltage sources and opening current sources effectively finds the 'Thevenin equivalent' looking into the network.. Option D is the inverse of the correct procedure and is fundamentally incorrect.

Answer: C is correct — Norton resistance is determined by shorting all independent voltage sources and opening all independent current sources.

Exam Tip: Remember: Voltage sources have internal resistance of 0 (short), while current sources have internal resistance of $\infty$ (open). This rule applies to both Thevenin and Norton resistance calculations.

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