Let , V be the potential difference across the two common points A and B. Then , from Ohm'* law
Current passing through R1, I1 = V/R1
Current passing through R2, I2 = V/R2
Current passing through R3, I3 = V/R3
If R is the equivalent resistance, then from Ohm'* law, the total current flowing through the circuit is given by,
I = V/R and I = I1 + I2 + I3
Now,
