Question

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)

This question was addressed to me during an interview for a job.

The query is from Star-Delta Transformation in division Useful Theorems in Circuit Analysis of Network Theory

Answer 1

The correct option is (c) (R1R2 + R2R3 + R3R1)/R2

The explanation is: 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.