Question

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)

I had been asked this question during an online exam.

The origin of the question is Star-Delta Transformation in chapter Useful Theorems in Circuit Analysis of Network Theory

Answer 1

Right option is (c) (R1R2 + R2R3 + R3R1)/R1

To explain: 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.