JEE Main 2025 Apr 4 Shift 2, Physics Q6: Introduction And Ohm’s Law

JEE Main2025Apr 4, Shift 2Physics

From the combination of resistors with resistance values $R_{1} = R_{2} = R_{3} = 5 Ω$ and $R_{4} = 10 Ω$ , which of the following combination is the best circuit to get an equivalent resistance of $6 Ω$ ?

Solution

Test option (1): the top branch is $R_{1} + R_{2} = 5 + 5 = 10 Ω$ , and the bottom branch is $R_{3} + R_{4} = 5 + 10 = 15 Ω$ . These two branches are in parallel:

$R_{e q} = \frac{10 \times 15}{10 + 15} = \frac{150}{25} = 6 Ω$ . $✓$

Quick checks rule out the others. Option (2) gives $(R_{1} + R_{2} + R_{4}) ∥ R_{3} = 20 ∥ 5 = 4 Ω$ . Option (4) is $5 ∥ 5 ∥ 5 ∥ 10$ — much less than $6 Ω$ . Option (3) does not yield $6 Ω$ either.

$∴$ Option (1) gives the required $6 Ω$ .

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JEE Main 2025 Apr 4 Shift 2, Physics Q6: Introduction And Ohm’s Law

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