A uniform metallic wire of length L and cross-sectional area A has resistance R. The wire is now stretched, without any change in temperature or loss of material, so that its length becomes 2L.
(i) Define electrical resistivity of a conductor.
(ii) Assuming the stretching is uniform and the volume of the wire remains constant, derive an expression for the new resistance R′ in terms of the original resistance R.
(iii) Give a qualitative explanation for the increase in resistance even though the resistivity of the material is unchanged.