Consider the following statements regarding Thevenin’s Theorem:1.Thevenin’s theorem states that any linear bilateral network can be replaced by an equivalent voltage source in series with a resistance.2.Thevenin resistance is calculated by deactivating all independent sources and finding equivalent resistance seen from terminals.3.The open circuit voltage across terminals is equal to Thevenin voltage of the network.4.Thevenin equivalent is valid only for DC circuits and cannot be applied to AC circuits.Which of the above statements is/are correct?

Correct Answer: C - 1, 2 and 3 only

Quick Concept Explanation

Thevenin's theorem replaces a linear two-terminal network by one voltage source Vth in series with an equivalent impedance. For a network with independent sources, Rth/Zth is found by suppressing independent sources; dependent sources remain and may require a test-source method. Key relation: V_th=V_OC; Z_th seen at the port with independent sources suppressed.

Exam focus: In AC, use impedances—not just resistances. Common trap: Dependent sources are not turned off when finding Thevenin resistance.

Statement-wise Verification

• Statement 1 - Correct.
  Thevenin’s theorem states that any linear bilateral network can be replaced by an equivalent voltage source in series with a resistance.
  Thevenin's theorem replaces a linear two-terminal network by one voltage source Vth in series with an equivalent impedance.
• Statement 2 - Correct.
  Thevenin resistance is calculated by deactivating all independent sources and finding equivalent resistance seen from terminals.
  V_th=V_OC; Z_th seen at the port with independent sources suppressed.
• Statement 3 - Correct.
  The open circuit voltage across terminals is equal to Thevenin voltage of the network.
  Vth is the open-circuit terminal voltage.
• Statement 4 - Incorrect.
  Thevenin equivalent is valid only for DC circuits and cannot be applied to AC circuits.
  Thevenin equivalence also applies in sinusoidal AC networks by using complex impedances

Core Concept

Thevenin's theorem replaces a linear two-terminal network by one voltage source Vth in series with an equivalent impedance. Vth is the open-circuit terminal voltage. For a network with independent sources, Rth/Zth is found by suppressing independent sources; dependent sources remain and may require a test-source method. The theorem applies to AC circuits using complex impedances as well as to DC circuits.

Formula / Key Relationship

V_th=V_OC; Z_th seen at the port with independent sources suppressed.

Why the Other Options Are Wrong

Option A is incorrect because it omits correct statement(s) 1. Option B is incorrect because it includes incorrect statement(s) 4 and omits correct statement(s) 2, 3. Option D is incorrect because it includes incorrect statement(s) 4.

Exam Shortcut / Approach

In AC, use impedances—not just resistances.

Common Mistake

Dependent sources are not turned off when finding Thevenin resistance.

Quick Revision

Thevenin Equivalent Network is linked with Thevenin's Theorem, Network Theorems and Network Theory. In AC, use impedances—not just resistances.