Which theorem allows replacing a circuit with an equivalent voltage source in series with a resistor?

Which theorem allows replacing a circuit with an equivalent voltage source in series with a resistor?

• A. Kirchhoff's Law
• B. Norton's Theorem
• C. Thevenin's Theorem
• D. Superposition

Answer: (C)

The concept being tested is the ability to simplify a complex, two-terminal network into a simple, equivalent form for easier loading analysis. Thevenin's theorem states that any linear circuit seen from two terminals can be replaced by a single voltage source in series with a resistor. The voltage source, Vth, is the open-circuit voltage at the terminals, and the series resistance, Rth, is the resistance seen when all independent sources are turned off (voltage sources shorted, current sources opened). This form makes it straightforward to determine how any connected load will behave, since you just compute the current or voltage using Vth and Rth. This is the best choice because it directly describes replacing a network with a voltage source in series with a resistor. The other concepts describe different ways to analyze circuits or different equivalent forms: Kirchhoff’s laws govern voltage and current sums around loops, Superposition lets you add the effects of each source separately, and Norton’s theorem provides a current source in parallel with a resistor—the dual form of Thevenin.

The concept being tested is the ability to simplify a complex, two-terminal network into a simple, equivalent form for easier loading analysis. Thevenin's theorem states that any linear circuit seen from two terminals can be replaced by a single voltage source in series with a resistor. The voltage source, Vth, is the open-circuit voltage at the terminals, and the series resistance, Rth, is the resistance seen when all independent sources are turned off (voltage sources shorted, current sources opened). This form makes it straightforward to determine how any connected load will behave, since you just compute the current or voltage using Vth and Rth.

This is the best choice because it directly describes replacing a network with a voltage source in series with a resistor. The other concepts describe different ways to analyze circuits or different equivalent forms: Kirchhoff’s laws govern voltage and current sums around loops, Superposition lets you add the effects of each source separately, and Norton’s theorem provides a current source in parallel with a resistor—the dual form of Thevenin.