(a) Explain qualitatively how the resistance of a metallic conductor depends on (i) its length and (ii) its cross-sectional area, keeping other factors the same.
(b) Two copper wires P and Q have the same length but the radius of Q is twice that of P. Without performing any calculation, state and justify which wire has the lower resistance.
(c) Both wires are stretched uniformly so that their lengths increase by 10 %. Comment on whether the percentage change in resistance is the same for P and Q, giving reasons for your answer.