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The resistivity os copper is `1.76 xx 10^-8` ohm m. The radius of the wire is `1 mm`. Calculate the length of a telegraph wire needed for having a resistance of `10.5 Omega`. |
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Answer» Correct Answer - `1.873 km` As `R = (rho l)/(A), l = (RA)/(rho) = (R(pi r^2))/(rho) = (10.5 Omega xx 3.14 xx (10^-3 m)^2)/(1.76 xx 10^-8 Omega m)=1.873 xx 10^3m = 1.873 km`. |
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