Question

Thirteen resistances each of resistance RΩ are connected in the circuit as shown in the figure the effective resistance between A and B is... 

(A) (2R)Ω

(B) (4R/3)Ω 

(C) (2R/3)Ω 

(D) R

Answer 1

The correct option (C) (2R/3)Ω

Explanation:

The circuit can be redrawn as here in every delta. R is in series with R

∴ Req = R + R = 2R.

hence it can be reduced as

∴ 2R || R given {(2R × R) / (2R + R)} = (2R / 3)

 ∴ R_AB = (4/3)R || (4/3)R

= [{(4/3)R × (4/3)R}/{(4/3)R + (4/3)R}]

= [{(16/9)R²}/{(8/3)R}]

 = (2R/3)Ω