This set of Network Theory Question Bank focuses on “Open Circuit Impedence(Z) Parameters”.

1. Two ports containing no sources in their branches are called?

a) active ports

b) passive ports

c) one port

d) three port

View Answer

Explanation: Two ports containing no sources in their branches are called passive ports; among them are power transmission lines and transformers.

2. Two ports containing sources in their branches are called?

a) three port

b) one port

c) passive ports

d) active ports

View Answer

Explanation: Two ports containing sources in their branches are called active ports. A voltage and current is assigned to each of the two ports.

3. In determining open circuit impedance parameters, among V_{1}, V_{2}, I_{1}, I_{2}, which of the following are dependent variables?

a) V_{1} and V_{2}

b) I_{1} and I_{2}

c) V_{1} and I_{2}

d) I_{1} and V_{2}

View Answer

Explanation: In determining open circuit impedance parameters, among V

_{1}, V

_{2}, I

_{1}, I

_{2}; V

_{1}and V

_{2}are dependent variables and I

_{1}, I

_{2}are independent variables i.e., dependent variables depend on independent variables.

4. In determining open circuit impedance parameters, among V_{1}, V2, I_{1}, I2, which of the following are independent variables?

a) I_{1} and V_{2}

b) V_{1} and I_{2}

c) I_{1} and I_{2}

d) V_{1} and V_{2}

View Answer

Explanation: In determining open circuit impedance parameters, among V

_{1}, V

_{2}, I

_{1}, I

_{2}; I

_{1}and I

_{2}are independent variables and V

_{1}, V

_{2}are dependent variables. Independent variables are the variables that do not depend on any other variable.

5. Which of the following expression is true in case of open circuit parameters?

a) V_{1} = Z_{11} V_{1} + Z_{12} I_{2}

b) V_{1} = Z_{11}I_{1} + Z_{12} V_{2}

c) V_{1} = Z_{11}I_{1} + Z_{12} I_{2}

d) V_{2} = Z_{11}I_{1} + Z_{12} I_{2}

View Answer

Explanation: The expression relating the open circuit parameters Z

_{11}, Z

_{12}and currents I

_{1}, I

_{2}and voltage V

_{1}is V

_{1}= Z

_{11}I

_{1}+ Z

_{12}I

_{2}.

6. Which of the following expression is true in case of open circuit parameters?

a) V_{2} = Z_{21}I_{2} + Z_{22} I_{2}

b) V_{2} = Z_{21}I_{1} + Z_{22} I_{2}

c) V_{1} = Z_{21}I_{2} + Z_{22} I_{2}

d) V_{1} = Z_{21}I_{1} + Z_{22} I_{2}

View Answer

Explanation: The expression relating the currents I

_{1}, I

_{2}and voltage V

_{1}and open circuit parameters Z

_{21}, Z

_{22}is V

_{2}= Z

_{21}I

_{1}+ Z

_{22}I

_{2}.

7. Find the Z – parameter Z_{11} in the circuit shown below.

a) 1

b) 1.5

c) 2

d) 2.5

View Answer

Explanation: For determining Z

_{11}, the current I

_{2}is equal to zero. Now we obtain Z

_{eq}as 1+ (6×2)/(6+2)=2.5Ω. So, Z

_{11}= 2.5Ω.

8. The value of Z_{21} in the circuit shown in the question 7 is?

a) 0

b) 1

c) 2

d) 3

View Answer

Explanation: V

_{2}is the voltage across the 4Ω impedance. The current through 4Ω impedance is I

_{1}/4. And V

_{2}= (I

_{1}/4) x 4 = I

_{1}. So, Z

_{21}= 1Ω.

9. Find the value of Z_{12} in the circuit shown in the question 7.

a) 3

b) 2

c) 1

d) 0

View Answer

Explanation: The current through vertical 2Ω resistor is = I

_{2}/2. So, V

_{1}= 2 x (I

_{2}/2). On solving and substituting we get Z

_{12}= 1Ω.

10. Determine the value of Z_{22} in the circuit shown in the question 7.

a) 0

b) 1

c) 2

d) 3

View Answer

Explanation: Open circuiting port 1, we get V

_{2}= I

_{2}((2+2)||4) => V

_{2}= I

_{2}x 2 =>V

_{2}/I

_{2}= 2. Therefore the value of Z

_{22}is 2Ω.

**Sanfoundry Global Education & Learning Series – Network Theory.**

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