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Electrical Engineering › Network Theory

Two-Port Networks MCQ [Free PDF] – 3 Objective Questions with Answers

Every Two-Port Networks question asked in GPSC DEE Electrical, GPSC AE Electrical — solve, check instantly, then read the formula and exam tip.

3 PYQs1 subtopic2 examsUpdated 23 Oct 2026
Topic practice0/3✓ 0✗ 0

Z Parameters (3)

Q1Moderate
Asked in: GPSC DEE Electrical · DEE Master paper · 2026
A two-port network has defined Z-parameters. Then
1. 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?
View answer & solution
Correct answer: A. All of the above
Quick 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.

V1 = Z11 I1 + Z12 I2; V2 = Z21 I1 + Z22 I2. Z11=(V1/I1)|I2=0, Z12=(V1/I2)|I1=0.
Verified · SRO editorial deskSolution page → Report
Q2Moderate
Asked in: GPSC DEE Electrical · DEE Master paper · 2026
A two-port network has Z11 = 20 Ω, Z22 = 10 Ω, Z12 = Z21 = 5 Ω. Then
1. Network is reciprocal.
2. Input impedance depends on load connected.
3. Z-parameters are valid for open-circuit conditions.
4. Z12 equals Z21 for symmetric networks only.
Which of the above statements is/are correct?
View answer & solution
Correct answer: C. 1, 2 and 3 only
Quick explanation

Z-parameters express two-port terminal voltages as linear combinations of port currents. Reciprocity requires Z12=Z21; symmetry additionally requires Z11=Z22. Key relation: V1=Z11I1+Z12I2; V2=Z21I1+Z22I2.

Exam focus: Reciprocal: Z12=Z21. Symmetric: Z11=Z22. Common trap: Do not confuse reciprocity with symmetry.

V1=Z11I1+Z12I2; V2=Z21I1+Z22I2.
Verified · SRO editorial deskSolution page → Report
Q3Hard
Asked in: GPSC AE Electrical · AE R&B · 2025 · Series M
This question uses a figure from the original paper. The figure is being added; the answer and explanation are already verified.
In the circuit shown below, find the Z-parameter Z₁₂.
View answer & solution
Correct answer: C. 5
Quick explanation

GPSC revised the final answer to option C. For Z-parameters, Z12 = V1/I2 with I1 = 0. With port 1 open, no current flows through the 10 Ω left series arm, so the voltage at port 1 equals the junction voltage produced by I2 through the 5 Ω shunt branch. Hence Z12 = 5 Ω.

V₁ = Z₁₁I₁ + Z₁₂I₂ Set I₁ = 0: Z₁₂ = V₁/I₂ = 5 Ω
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