Question

Using Kirchhoff’s rules determine the value of unknown resistance R in the circuit so that no current flows through 4 Ω resistance. Also find the potential difference between A and D.

Answer 1

Apply Kirchhoff’s In loop ABCFA:-

I + I + 4I₁ = 9 − 6

2I + 4I₁ = 3 … (1)

As there is no current flowing through the 4Ω resistance,

I₁ = 0

Or, 2I = 3

Or, I = 1.5A

Thus the current through resistances R is 1.5A.

As there is no current through branch CF, thus equivalent circuit will be,

By applying Kirchhoff’s loop law we get,

1.5 + 1.5 + R (1.5) = 9 − 3

R = 2Ω

Potential difference between A and D = (9 − 3) = 6V