InterviewSolution
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InterviewSolution
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A cell of constant e.m.f. first connected to a resistance `R_(1)` and then connected to a resistance `R_(2)`. If power delivered in both cases is then the internal resistance o f the cell isA. `sqrt(R_(1) + R_(2))`B. `sqrt((R_(1))/(R_(2)))`C. `(R_(1) - R_(2))/(2)`D. `(R_(1) + R_(2))/(2)` |
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Answer» Correct Answer - A (a) Power dissipated `= i^(2) R = ((E)/(R + r))^(2) R` `:. ((E)/(R_(1) + r))^(2) R_(1) = ((E)/(R_(2) + r))^(2) R_(2)` `implies R_(1) (R_(1)^(2) + r_(2) + 2 R_(2) r) = R_(2) (R_(1)^(2) + r^(2) + 2 R_(1) r)` `implies R_(2)^(2) R_(1) + R_(1) r^(2) + 2 R_(2) r = R_(1)^(2) R_(2) + R_(2) r^(2) + 2 R_(1) R_(2) r` `implies (R_(1) - R_(2)) r^(2) = (R_(1) - R_(2)) r^(2) = (R_(1) - R_(2)) R_(1) R_(2)` `implies r = sqrt(R_(1) R_(2))` |
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