Norton's Theorem. Easy Step by Step Procedure with Example (Pictorial Views) This is another useful theorem to analyze electric circuits like Thevenin's Theorem, which reduces linear, active circuits and complex networks into a simple equivalent circuit. The main difference between Thevenin’s theorem and Norton’s theorem is that, Thevenin's theorem provides an equivalent voltage source and an equivalent series resistance, while Norton's theorem provides an equivalent Current source and an equivalent parallel resistance. Norton's theorem may be stated under: Any Linear Electric Network or complex circuit with Current and Voltage sources can be replaced by an equivalent circuit containing of a single independent Current Source IN and a Parallel Resistance RN.