A wire of 10-ohm resistance stretched to thrice its original length. What will be its 1) new resistivity 2) new resistance

Resistivity is the property of the material and it will not change with changing the length of the wire.

(i) Since resistivity depends on the nature of the material of wire and is independent of dimensions of wire, so the resistivity remains unchanged.
(ii) In both cases, the volume of the wire is the same.

V = Al

R = ρl/A

R’ = 9ρl/A = 9R

R’ = 9*10= 90Ω

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