According to network theorems in electrical engineering, Norton's theorem replaces any linear two-terminal network by which form of equivalent source-and-impedance model?

Introduction / Context:
Norton's theorem is a cornerstone of circuit simplification in electrical engineering. It allows you to replace any linear, bilateral two-terminal network (containing independent/dependent sources and resistances/impedances) with an equivalent model that is easier to analyze—especially for varying loads and parallel interconnections.

Given Data / Assumptions:

• The original network is linear and time-invariant.
• All frequency-domain impedances are allowed (R, L, C) as a single equivalent impedance.
• The theorem is applied at a specific pair of output terminals.

Concept / Approach:

Norton's theorem states that a two-port seen from its output terminals is equivalent to a current source IN in parallel with an impedance RN (also written ZN). IN is the short-circuit current at the terminals, and RN equals the Thevenin resistance RTH (found by deactivating independent sources, or by test-source methods when dependent sources are present).

Step-by-Step Solution:

Verification / Alternative check:

Convert between Thevenin and Norton to verify: VTH = IN * RN and RTH = RN. Analyzed with any load RL, the Norton and Thevenin forms yield identical terminal currents and voltages.

Why Other Options Are Wrong:

'Voltage source in series with impedance' is Thevenin, not Norton. 'Current source in series with impedance' is not a standard canonical form. 'Voltage source in parallel with impedance' also does not match Norton's canonical form.

Common Pitfalls:

Confusing IN with load current (IN is the short-circuit current), and forgetting that RN equals RTH. Also, failing to treat dependent sources correctly when computing RN.

Final Answer:

an equivalent current source in parallel with an equivalent impedance