250+ TOP MCQs on Star-Delta Transformation and Answers

Network Theory Questions on “Star-Delta Transformation”.

1. If a resistor R_x is connected between nodes X and Y, R_y between X and Y, R_z between Y and Z to form a delta connection, then after transformation to star, the resistor at node X is?
A. R_xR_y/(R_x+R_y+R_z)
B. R_xR_z/(R_x+R_y+R_z)
C. R_zR_y/(R_x+R_y+R_z)
D. (R_x+R_y)/(R_x+R_y+R_z)

Answer: A
Clarification: After transformation to star, the resistor at node X is R_xR_y/(R_x+R_y+R_z) and this resistance lies between R_x, R_y in star connection.

2. If a resistor R_x is connected between nodes X and Y, R_y between X and Y, R_z between Y and Z to form a delta connection, then after transformation to star, the resistance at node Y is?
A. R_zR_y/(R_x+R_y+R_z)
B. R_zR_x/(R_x+R_y+R_z)
C. R_xR_y/(R_x+R_y+R_z)
D. (R_z+R_y)/(R_x+R_y+R_z)

Answer: B
Clarification: After transformation to star, the resistor at node Y is R_zR_x/(R_x+R_y+R_z) and this resistance lies between R_x, R_z in star connection.

3. If a resistor R_x is connected between nodes X and Y, R_y between X and Y, R_z between Y and Z to form a delta connection, then after transformation to star, the resistance at node Z is?
A. R_yR_x/(R_x+R_y+R_z)
B. R_yR_x/(R_x+R_y+R_z)
C. R_zR_y/(R_x+R_y+R_z)
D. (R_z+R_x)/(R_x+R_y+R_z)

Answer: C
Clarification: After transformation to star, the resistor at node Y is R_zR_y/(R_x+R_y+R_z) and this resistance lies between R_z, R_y in star connection.

4. If the resistors of star connected system are R₁, R₂, R₃ then the resistance between 1 and 2 in delta connected system will be?
A. (R₁R₂ + R₂R₃ + R₃R₁)/R₃
B. (R₁R₂ + R₂R₃ + R₃R₁)/R₁
C. (R₁R₂ + R₂R₃ + R₃R₁)/R₂
D. (R₁R₂ + R₂R₃ + R₃R₁)/(R₁+R₂)

Answer: A
Clarification: After transformation to delta, the resistance between 1 and 2 in delta connected system will be (R₁R₂ + R₂R₃ + R₃R₁)/R₃ and this resistance lies between R₁, R₂ in delta connection.

5. If the resistors of star connected system are R₁, R₂, R₃ then the resistance between 2 and 3 in delta connected system will be?
A. (R₁R₂ + R₂R₃ + R₃R₁)/R₃
B. (R₁R₂ + R₂R₃ + R₃R₁)/R₂
C. (R₁R₂ + R₂R₃ + R₃R₁)/R₁
D. (R₁R₂ + R₂R₃ + R₃R₁)/(R₃+R₂)

Answer: C
Clarification: After transformation to delta, the resistance between 2 and 3 in delta connected system will be (R₁R₂ + R₂R₃ + R₃R₁)/R₁ and this resistance lies between R₃, R₂ in delta connection.

6. If the resistors of star connected system are R₁, R₂, R₃ then the resistance between 3 and 1 in delta connected system will be?
A. (R₁R₂ + R₂R₃ + R₃R₁)/R₁
B. (R₁R₂ + R₂R₃ + R₃R₁)/R₃
C. (R₁R₂ + R₂R₃ + R₃R₁)/R₂
D. (R₁R₂ + R₂R₃ + R₃R₁)/(R₃+R₁)

Answer: C
Clarification: After transformation to delta, the resistance between 2 and 3 in delta connected system will be (R₁R₂ + R₂R₃ + R₃R₁)/R₂ and this resistance lies between R₁, R₃ in delta connection.

7. Find the equivalent resistance at node A in the delta connected circuit shown in the figure below.

A. 1
B. 2
C. 3
D. 4

Answer: D
Clarification: Performing delta to star transformation we obtain the equivalent resistance at node A is R =(11×12)/(11+12+13)=4Ω.

8. Find the equivalent resistance at node C in the delta connected circuit shown below.

A. 3.66
B. 4.66
C. 5.66
D. 6.66

Answer: B
Clarification: Performing delta to star transformation we obtain the equivalent resistance at node A is R =(12×13)/(11+12+13)=4.66Ω.

9. Find the equivalent resistance between node 1 and node 3 in the star connected circuit shown below.

A. 30
B. 31
C. 32
D. 33

Answer: C
Clarification: The equivalent resistance between node 1 and node 3 in the star connected circuit is R =(10×10+10×11+11×10)/10=32Ω.

10. Find the equivalent resistance between node 1 and node 2 in the star connected circuit shown below.

A. 2
B. 29
C. 30
D. 31

Answer: B
Clarification: The equivalent resistance between node 1 and node 3 in the star connected circuit is R =(10×10+10×11+11×10)/11=29Ω.