Question

In the circuit shown in Fig, all wires have equal resistance r. Find the equivalent resistance between A and B. 

Answer 1

Path ADCB is similar to path AFEB

⇒ i_AD = i_ET

Where i_AD is current trough RAD. 

⇒ V_D = V_F

⇒ V_FD = D

⇒ Resistor FD can be removed 

Similar EC can be removed 

R_ADCB = 3r

R_DFEB = 3r

R_AB = r 

Let effective resistance be R_eff.