This set of Network Theory Multiple Choice Questions & Answers (MCQs) focuses on “Short Circuit Admittance(Y) Parameters”.

1. In determining short circuit impedance parameters, among V1, V2, I1, I2, which of the following are dependent variables?
a) V1 and V2
b) I1 and I2
c) V1 and I2
d) I1 and V2

Explanation: In determining short circuit impedance parameters, among V1, V2, I1, I2; I1 and I2 are dependent variables and V1, V2 are independent variables i.e., dependent variables depend on independent variables.

2. In determining short circuit impedance parameters, among V1, V2, I1, I2, which of the following are independent variables?
a) I1 and V2
b) V1 and I2
c) I1 and I2
d) V1 and V2

Explanation: In determining short circuit impedance parameters, among V1, V2, I1, I2; V1 and V2 are independent variables and I1, I2 are dependent variables. Independent variables are the variables that do not depend on any other variable.

3. Which of the following expression is true in case of short circuit parameters?
a) I1 = Y11 V1 + Y12 V2
b) I1 = Y11 I1 + Y12 V2
c) V1 = Y11 I1 + Y12 V2
d) V1 = Y11 V1 + Y12 V2

Explanation: The expression relating the short circuit parameters Y11, Y12 and voltages V1, V2 and current is I1, is I1 = Y11 V1 + Y12 V2.

4. Which of the following expression is true in case of short circuit parameters?
a) I2 = Y21I1 + Y22 I2
b) V2 = Y21I1 + Y22 V2
c) I2 = Y21V1 + Y22 V2
d) I2 = Y21V1 + Y22 I2

Explanation: The expression relating the voltages V1, V2 and current is I2 and short circuit parameters Y11, Y12 is I2 = Y21V1 + Y22V2.

5. The parameters Y11, Y12, Y21, Y22 are called?
a) Open circuit impedance parameters
c) Inverse transmission parameters
d) Transmission parameters

Explanation: The parameters Y11, Y12, Y21, Y22 are called short circuit admittance parameters also called network functions as they are obtained by short circuiting port 1 or port 2.
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6. Find the Y – parameter Y11 in the circuit shown below.

a) 2
b) 3/2
c) 1
d) 1/2

Explanation: After short circuiting b-b’, the equation will be V1 = (I1) x 2. We know Y11 = I1/V1. From the equation we get I1/V1 = 2. On substituting we get Y11 = 2 mho.

7. Find the Y – parameter Y21 in the circuit shown below.

a) -1/4
b) 1/4
c) 1/2
d) -1/2

Explanation: After short circuiting b-b’, the equation will be -I2=I1 × 2/4=I1/2 and -I2 = V1/4 and on solving and substituting we get Y21 = I2/V1=-1/4 mho.

8. Find the Y – parameter Y22 in the circuit shown below.

a) 3/8
b) 5/8
c) 7/8
d) 9/8

Explanation: On short circuiting a-a’, we get Zeq = 8/5 Ω. V2=I2× 8/5. We know Y22 = I2/V2. We got I2/V1 = 5/8. ON substituting we get Y22 = 5/8 mho.

9. Find the Y – parameter Y12 in the circuit shown below.

a) 1/2
b) -1/2
c) -1/4
d) 1/4

Explanation: Short circuiting a-a’, -I1 = 2/5 I2 and I2 = 5 V2/8. On solving -I1 = 2/5×5/8 V2 = V2/4. We know Y12 = I1/V2. We got I1/V2 = -1/4. So the value of Y12 will be -1/4 mho.

10. Which of the following equation is true in the circuit shown below?

a) I1=0.5(V1)+0.25(V2)
b) I1=0.25(V1)+0.625(V2)
c) I1=-0.25(V1)+0.625(V2)
d) I1=0.5(V1)-0.25(V2)

Explanation: We got the admittance parameters as Y11 = 0.5, Y12 = -0.25, Y21 = -0.25, Y22 = 0.625. So the equations in terms of admittance parameters is I1=0.5(V1)-0.25(V2) and I2=-0.25(V1)+0.625(V2).

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