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A copper wire is stretched to make it 0.2% longer. What is the percentage change in its resistance? |
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Answer» The mass m of the wire of length l, area of cross section A and density d is givne by `m=Ald or A=(m)/(ld)` The resistance R of the wire of resistivity `rho` is given by `R= (rho l)/(A) = (rho l^(2)d)/(m)= k l^(2)` Where `k=(rho d)//(m)` is a constant of the wire. `:. (dR)/(R) xx 100 = (2 xx 0.2)/(100) xx 100=0.4%`. |
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