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What is the minimum resistance which can be made using five resistors each of 1/5 Ω? (a) 1/5 Ω (b) 1/25 Ω (c) 1/10 Ω (d) 25 Ω |
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Answer» The answer is (b) 1/25 Ω Minimum resistance is obtained when resistors are connected parallel 1 /R = 5 + 5 + 5 +5 +5 = 25 Ω R = 1/25 You know, equivalent resistance decreases when resistors are joined in parallel.e.g., 1/Req = 1/R₁ + 1/R₂ + 1/R₃ + 1/R₄ + ....... + 1/Rn . While equivalent resistance increases when resistors are joined in series e.g., Req = R₁ + R₂ + R₃ + .... + Rn. it Means, we can get minimum resistance when all the given resistors will join in parallel. And we can get maximum resistance when all the resistors will join in series . ∴ for finding minimum resistance , we have to join all resistors in parallel. So , 1/Req = 1/(1/5) + 1/(1/5) + 1/(1/5) + 1/(1/5) + 1/(1/5) 1/Req = 5 + 5 + 5 + 5 + 5 = 25 Req = 1/25 Ω Hence , minimum resistance = 1/25 Ω |
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