Star Delta Transformation MCQ [Free PDF] – Objective Question Answer for Star Delta Transformation Quiz

1. Find the equivalent delta circuit in Star − Delta Transformation.

A. 9.69 ohm, 35.71 ohms, 6.59 ohm
B. 10.69 ohm, 35.71 ohms, 6.59 ohm
C. 9.69 ohm, 34.71 ohms, 6.59 ohm
D. 10.69 ohm, 35.71 ohms, 7.59 ohm

Using the star to delta conversion:

R1  = 4.53 + 6.66 + 4.53 × 6.66/1.23 = 35.71 ohm
R2  = 4.53 + 1.23 + 4.53 × 1.23/6.66 = 6.59 ohm
R3  = 1.23 + 6.66 + 1.23 × 6.66/4.53 = 9.69 ohm.

2. Which, among the following is the correct expression for star − delta conversion?

1.  R1 = Ra × Rb/(Ra + Rb + RC., R2 = Rb × Rc/(Ra + Rb + RC., R3 = Rc × Ra/(Ra + Rb + RC.B.
2. R1 = Ra/(Ra + Rb + RC., R2 = Rb/(Ra + Rb + RC., Rc = /(Ra + Rb + RC.
3. R1 = Ra + Rb + Ra × Rb/Rc, R2 = Rc + Rb + Rc × Rb/Ra, R3 = Ra + Rc + Ra × Rc/Rb
4. R1 = Ra × Rb/Rc, R2 = Rc × Rb/Ra, R3 = Ra × Rc/Rb

After converting to delta, each delta connected resistance is equal to the sum of the two resistance it is connected to the + product of the two resistances divided by the remaining resistance. Hence

R1 = Ra + Rb + Ra × Rb/Rc
R2 = Rc + Rb + Rc × Rb/Ra
R3 = Ra + Rc + Ra × Rc/Rb.

3. Find the equivalent resistance between X and Y using star-delta transformation.

A. 3.33 ohm
B. 4.34 ohm
C. 5.65 ohm
D. 2.38 ohm

The 3 2ohm resistors are connected in star, changing them to delta, we have

R1 = R2 = R3 = 2 + 2 + 2 × 2/2 = 6 ohm.

The 3 6ohm resistors are connected in parallel to the 10 ohms 5 ohm and 10ohm resistors respectively.

This network can be further reduced to a network consisting of a 3.75ohm and 2.73ohm resistor connected in series whose resultant is intern connected in parallel to the 3.75 − ohm resistor.

4. Delta connection is also known as____________

A. Y − connection
B. Mesh connection
C. Either Y − connection or mesh connection
D. Neither Y − connection nor mesh connection

Delta connection is also known as mesh connection because its structure is like a mesh, that is, a planar closed-loop.

5. Ra is resistance at A, Rb is resistance at B, and Rc is resistance at C in star connection. After transforming to delta, what is the resistance between B and C?

A. Rc + Rb + Rc × Rb/Ra
B. Rc + Rb + Ra × Rb/Rc
C. Ra + Rb + Ra × Rc/Rb
D. Rc + Rb + Rc × Ra/Rb

After converting to the delta, each delta connected resistance is equal to the sum of the two resistances it is connected to the + product of the two resistances divided by the remaining resistance.

Hence, resistance between B and C

= Rc + Rb + Rc × Rb/Ra.

6. Ra is resistance at A, Rb is resistance at B, and Rc is resistance at C in star connection. After transforming to delta, what is the resistance between A and C?
A. Ra + Rb + Ra × Rb/Rc
B. Ra + Rc + Ra × Rc/Rb
C. Ra + Rb + Ra × Rc/Ra
D. Ra + Rc + Ra × Rb/Rc

After converting to the delta, each delta connected resistance is equal to the sum of the two resistances it is connected to the + product of the two resistances divided by the remaining resistance.

Hence, the resistance between A and C

= Ra + Rc + Ra × Rc/Rb.

7. Ra is resistance at A, Rb is resistance at B, and Rc is resistance at C in star connection. After transforming to delta, what is the resistance between A and B?

A. Rc + Rb + Ra × Rb/Rc
B. Ra + Rb + Ra × Rc/Rb
C. Ra + Rb + Ra × Rb/Rc
D. Ra + Rc + Ra × Rc/Rb

After converting to the delta, each delta connected resistance is equal to the sum of the two resistances it is connected to the + product of the two resistances divided by the remaining resistance.

Hence, resistance between A and B = Ra + Rb + Ra × Rb/Rc.

8. If a 1ohm 2ohm and 32/3ohm resistor is connected in star, find the equivalent delta connection.

A. 34 ohm, 18.67 ohms, 3.19 ohm
B. 33 ohm, 18.67 ohms, 3.19 ohm
C. 33 ohm, 19.67 ohms, 3.19 ohm
D. 34 ohm, 19.67 ohms, 3.19 ohm

Using the formula for delta to star conversion:
Using the formula for delta to star conversion:
R1 = 1 + 2 + 1 × 2/(32/3)
R2 = 1 + 32/3 + 1 × (32/3)/2
R3 = 2 + 32/3 + 2 × (32/3)/1.

9. If an 8/9ohm, 4/3ohm, and 2/3ohm resistor are connected to the star, find its delta equivalent.

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

Using the formula for the star to delta conversion:

R1 = 8/9 + 4/3 + (8/9) × (4/3)/(2/3)
R2 = 8/9 + 2/3 + (8/9) × (2/3)/(4/3)
R3 = 2/3 + 4/3 + (2/3) × (4/3)/(8/9).

10. Find the equivalent resistance between A and B  using star-delta transformation.

A. 32ohm
B. 31ohm
C. 30ohm
D. 29ohm