Question

In the given circuit the equivalent resistance between the points A and B in ohm is. 

(A) 9 

(B) 11.6 

(C) 14.5 

(D) 21.2

Answer 1

The correct option (B) 11.6 

Explanation:

3Ω in series with 2Ω = 3 + 2 = 5Ω

This 5Ω is parallel to 6Ω

 ∴ R' = {(5 × 6)/(5 + 6)} = (30/11)Ω

This R' will be in series with 7Ω

hence R" = 7 + (30/11) = (107/11)Ω

circuit can be redrawn as

Here

R_AB = 9Ω series with parallel combination of 5Ω, RΩ, (107 / 11)Ω

∴ R_AB = 9 [(1/5) + (1/12) + {1/(107/11)}]^–1

 = 9 [(1/5) + (1/12) + (11/107)]^–1

= 9 + {1/(0.38)}

= 9 + 2.58

= 11.58Ω

= 11.6Ω