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11 kW of electric power can be transmitted to a distant station at (i) 220 V or (ii) 22,000 V. Which of the two modes of transmission should be preferred and why ? Support your answer with possible calculations. |
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Answer» Solution : We shall prefer transmission of power to a distant STATION at 22,000 V in order to minimise power loss due to Joule.s heating during transmission. To explain it, let US PRESUME that resistance of transmission line be `R OMEGA`. When 11 kW (or `11 xx 10^(3)` W) power is transmitted at 220 V, line current `I = P/V = (11 xx 10^(3))/220 = 50 A` and power loss `=I^(2)R = (50)^(2) R = 2500 RW` However, when same power is transmitted at 22,000 V, the line current `I. = P/(V.) = (11 xx 10^(3))/(22,000) = 1/2 A = 0.5 A` Hence, power ions now `=I^(2) R = (0.5)^(2) xx R = 0.25 R W`. From above calculations, it is self-evident that the power loss in second option is negligible and THEREFORE we prefer this mode of power transmission. |
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