Practice portal › Current Electricity › Combination of Resistors

In the given figure switches S₁ and S₂ are in open condition. The resistance across ab when the switches S₁ and S₂ are closed is ______ Ω. [Figure: between a and b two parallel branches. Upper branch: 12 Ω, 4 Ω, 6 Ω in series. Lower branch: 6 Ω, 4 Ω, 12 Ω in series. S₁ joins the upper junction after 12 Ω to the lower junction after 6 Ω; S₂ joins the upper junction after 4 Ω to the lower junction after the lower 4 Ω.]

Asked in JEE Main 20th July 2nd Shift 2021 · Series and parallel combinations

Figure: Series and parallel combinations
Answer: 10

Step-by-step solution

With both switches closed the matching junctions merge, giving three parallel pairs in series.

First pair: 12∥6=4 Ω.

Second pair: 4∥4=2 Ω.

Third pair: 6∥12=4 Ω.

R_ab=4+2+4=10 Ω.

More Combination of Resistors questionsAll Combination of Resistors questions →

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.

Practise this with a timer