InterviewSolution
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InterviewSolution
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Two wires of equal length, one of aluminium and the other of copper have the same resistance. Which of the two wires is lighter ? Hence explain why aluminium wires are preferred for overhead power cables.(rho_(Al) = 2.63 xx 10^(-8) Omega m , rho_(Cu) = 1.72 xx 10^(-8) Omega m, Relative density of Al = 2.7 , of Cu = 8.9 ) |
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Answer» Solution :Light weight CABLES are chosen for overhead power cables. If VOLUME density of MASS for GIVEN wire is d then, `d = (m)/(V) = (m)/(Al) = (m)/(((rho L)/(R))l)"" (because R = (rho l)/(A) rArr A = (rho l)/(R) )` `therefore d = (mR)/(rho l^(2)) ` ` therefore m = (rho l^(2) d)/(R)` Here for given wires I and R are same and so, m `proprho`d `therefore (m_(1) )/(m_(2)) = (rho_(1) d_(1))/(rho_(2) d_(2))` Taking aluminium and copper wires as first and second wire respectively, `(m_(1))/(m_(2)) =((2.63 xx 10^(-8))( 2.7 xx 10^(3)))/((1.72 xx 10^(-8) ) (8.9 xx 10^(3)))` ` therefore (m_(1))/(m_(2))` = 0.4638 `therefore m_(1) lt m_(2)` Aluminium wire is lighter than copper wire. Hence, aluminium wires are chosen as overhead power cables. |
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