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.
a. (i) Define electrical resistivity of a conductor.
b. (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.
c. (iii) Give a qualitative explanation for the increase in resistance even though the resistivity of the material is unchanged.