Three conducting materials P, Q and R have resistivity values 2.0×10−8Ωm, 6.8×10−7Ωm and 1.6×10−6Ωm respectively.
(i) Arrange the materials in increasing order of electrical conductivity.
(ii) Which material would you recommend for making a 200m long overhead transmission line? Give one reason for your choice.
(iii) The selected material in part (ii) is drawn into a wire of cross-sectional area 3.0×10−6m2. Calculate the resistance offered by the entire length of this wire.