Q 12-03-202JEE MainJEE Main 2021 (20 Jul, Shift 2)Easy
In the given figure switches $S_1$ and $S_2$ are in open condition. The resistance across $ab$ when the switches $S_1$ and $S_2$ are closed is ______ $\Omega$.
Numerical value type. Enter your answer.
Answer: 10
With both switches closed the two rows are joined after each pair of resistors, giving three parallel pairs in series:
$$R_{ab} = (12\parallel6) + (4\parallel4) + (6\parallel12) = 4 + 2 + 4 = 10\ \Omega$$
Solution by Sreeraj P, M.Sc Physics