A copper wire of original length l and cross-sectional area A has resistance R. The wire is then stretched carefully so that its length becomes 2l while no material is lost.
a. (i) State the mathematical relation that connects the resistance of a uniform conductor with its length and cross-sectional area.
b. (ii) Keeping the volume of the wire constant, explain qualitatively how its cross-sectional area changes when the length is doubled.
c. (iii) Using appropriate reasoning, state whether the resistivity of the material changes during the stretching process. Give a brief justification.