InterviewSolution
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InterviewSolution
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A wire of length L and 3 identical cells of negligible internal resistance are connected in series. Due to the current, the temperature of the wire is raised by `DeltaT` in a time t. A number N of similar cells is now connected in series with a wire of the same material and cross-section but of length 2L. The temperature of the wire is raised by the same amount `DeltaT` in the same time t. the value of N isA. 4B. 6C. 8D. 9 |
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Answer» Correct Answer - B (b) Let `R` and `m` the resistance and mass of the first wire, then the second wire has resistance `2R` and mass `2 m`. Let `E =` emf of each cell, `S =` specific heat capacity of the material of the wire. For the first wire, current `i_(1) = (3 E)/(R )` and `i_(2) = (NE)/(2R) = mS Delta T` For the second wire, `i_(2) = (NE)/(2R)` and `i_(2)^(2) (2 R) t = 2 m S Delta T`. Thus, `i_(1) = i_(2)` or `N = 6`. |
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