A two-port network has defined Z-parameters. Then1.Defined under open-circuit conditions.2.Z11 represents input impedance.3.Z12 represents transfer impedance.4.Can be used in network interconnections.Which of the above statements is/are correct?

Correct Answer: A - All of the above

Quick Concept Explanation

For a linear two-port, terminal voltages are expressed in terms of terminal currents. Open-circuiting a port forces its current to zero and isolates the required coefficient. Key relation: V1 = Z11 I1 + Z12 I2; V2 = Z21 I1 + Z22 I2. Z11=(V1/I1)|I2=0, Z12=(V1/I2)|I1=0.

Exam focus: Memorize the condition “Z → open circuit (I=0)” and “Y → short circuit (V=0)”. Common trap: Do not label Z12=Z21 as symmetry; that equality is the reciprocity condition.

Statement-wise Verification

• Statement 1 - Correct.
  Defined under open-circuit conditions.
  Z-parameters are determined using open-circuit conditions because the defining current at the other port is set to zero.
• Statement 2 - Correct.
  Z11 represents input impedance.
  Z11 = V1/I1 with I2=0, so it is the driving-point/input impedance at port 1 under output open circuit.
• Statement 3 - Correct.
  Z12 represents transfer impedance.
  Z12 = V1/I2 with I1=0 is a transfer impedance (reverse transfer impedance in the usual port convention).
• Statement 4 - Correct.
  Can be used in network interconnections.
  Two-port parameter sets are used to analyze interconnected networks; Z-parameters are especially convenient for series-type interconnections and general two-port modeling.

Core Concept

For a linear two-port, terminal voltages are expressed in terms of terminal currents. Each Z coefficient has units of ohms. Open-circuiting a port forces its current to zero and isolates the required coefficient. Do not confuse the separate ideas of reciprocity and symmetry: reciprocity requires Z12=Z21, whereas symmetry requires Z11=Z22.

Formula / Key Relationship

V1 = Z11 I1 + Z12 I2; V2 = Z21 I1 + Z22 I2. Z11=(V1/I1)|I2=0, Z12=(V1/I2)|I1=0.

Step-by-Step Check

Independent check of the defining equations makes statements 1–3 direct identities. Statement 4 is a valid application of two-port parameters. Hence all four are correct and option A is the only complete choice.

Why the Other Options Are Wrong

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

Answer-Key Verification Note

The uploaded provisional key marks C . After independent technical verification, the defensible answer is A . This discrepancy is stated explicitly rather than silently copying the provisional key.

Exam Shortcut / Approach

Memorize the condition “Z → open circuit (I=0)” and “Y → short circuit (V=0)”.

Common Mistake

Do not label Z12=Z21 as symmetry; that equality is the reciprocity condition.

Quick Revision

Impedance Parameters is linked with Z-Parameters, Two-Port Networks and Network Theory. Memorize the condition “Z → open circuit (I=0)” and “Y → short circuit (V=0)”.