A wire of `10 Omega` resistance is stretched to thrice its original length. What will be its (i) new resistivity and (ii) new resistance?
Text Solution
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(i) Since resistivity depends on the nature of material of wire and is independent of dimensoins of wire, so the resistivity remains unchanged. (ii) In both the cases, the volume of the wire is same. So `V=Al = A'l' or A'= (lA)/(l') = (lA)/(3l)=(A)/(3)` Now `R= (rho l)/(A)` and `R'= (rho l')/(A')= (rho 3 l)/(A//3) =(9 rho l)/(A) =9R` `:. R' =9xx10= 90 Omega`
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