A bridge circuit is shown in the diagram. The equivalent resistance between A and B is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 4 Ω
$\text{Bridge check: } \frac{2}{4} = \frac{4}{8} = \frac{1}{2}$
$\text{Balanced bridge} \Rightarrow \text{no current through } 7\Omega$
$\text{Top branch: } 2 + 4 = 6\Omega$
$\text{Bottom branch: } 4 + 8 = 12\Omega$
$R_{\text{eq}} = \frac{6 \times 12}{6 + 12}$
$R_{\text{eq}} = \frac{72}{18} = 4\Omega$
The equivalent resistance is $4 \ \Omega$.