What is Norton’s Theorem and how does it relate to Thevenin’s?

• A. Any linear network can be replaced by a current source I_n in parallel with R_n; Thevenin and Norton are equivalent representations.
• B. The Norton theorem states that only voltage sources can be used in equivalent circuits.
• C. Norton’s theorem applies only to nonlinear networks.
• D. Norton and Thevenin representations are not related.

Answer: (A)

Norton’s Theorem says that any linear network seen from its terminals can be replaced by a current source in parallel with a resistor. The current source value is the short-circuit current that would flow if the terminals were tied together, and the parallel resistance is the resistance the network presents with all independent sources turned off. This viewpoint lets you analyze how the network drives a load by focusing on a single current and a single parallel resistance.

This sits alongside Thevenin’s theorem, which does the same kind of replacement but with a voltage source in series with a resistor. The two representations are interchangeable for the same external load: V_th equals I_N times R_N, and the equivalent resistance is the same in either form. In other words, you can convert between Norton and Thevenin without changing the terminal behavior of the network.