Circuit theorems are fundamental principles and mathematical techniques utilized in the analysis and solution of electrical circuits.

Any linear circuit can be reduced to an equivalent circuit with a single current source and a parallel resistance connected to a load.

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It is the curret supplied by the source which will pass through two selected terminals, when they are short circuited. I

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It is generally known equivalent resistance of the network as viewed from two selected terminals

Ohm's Law, a cornerstone of circuit analysis, establishes the relationship between current, voltage, and resistance.

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– Remove the resistance if any across two given points and short circuit them. – Calculate the current which will flow through the circuit. It is called Norton’s current and is written as Isc.

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Find the resistance Ri of the whole network as viewed from terminals AB, into the circuit when all the voltage sources have been removed by short circuits and replaced by their internal resistances.

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An illustrative example walks through the application of Norton's Theorem to determine the current in a 20Ω resistor.

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