Question

The electrical resistivity of five substances A, B, C, D and E are given below : A : 5.20 × 10-8 Ω m B : 110 × 10-8 Ω m C : 2.60 × 10-8 Ω m D : 10.00 × 10-8 Ω m E : 1.70 × 10-8 Ω m (a) Which substance is the best conductor of electricity? Why? (b) Which one is a better conductor: A or C? Why? (c) Which substance would you advise to be used for making heating elements of electric irons? Why? (d) Which two substances should be used for making electric wires? Why?

Answer 1

$$\begin{gathered} \mathrm{A}=5.20\times {10}^{-8}\mathrm{ohm}-\mathrm{m} \\ \mathrm{B}=110\times {10}^{-8}\mathrm{ohm}-\mathrm{m} \\ \mathrm{C}=2.60\times {10}^{-8}\mathrm{ohm}-\mathrm{m} \\ \mathrm{D}=10\times {10}^{-8}\mathrm{ohm}-\mathrm{m} \\ \mathrm{E}=1.70\times {10}^{-8}\mathrm{ohm}-\mathrm{m} \\ \left(\mathrm{a}\right)\mathrm{E}\mathrm{is}\mathrm{the}\mathrm{best}\mathrm{conductor}\mathrm{of}\mathrm{electricity}. \\ \left(\mathrm{b}\right)\mathrm{C}\mathrm{is}\mathrm{better}\mathrm{conductor}\mathrm{because}\mathrm{it}\mathrm{has}\mathrm{low}\mathrm{resistivity}\mathrm{than}\mathrm{A}. \\ \left(\mathrm{c}\right)\mathrm{B}\mathrm{is}\mathrm{used}\mathrm{for}\mathrm{making}\mathrm{heating}\mathrm{elements}\mathrm{of}\mathrm{electric}\mathrm{irons}\mathrm{because}\mathrm{it}\mathrm{has}\mathrm{high}\mathrm{electrical}\mathrm{resistivity}. \\ \left(\mathrm{d}\right)\mathrm{C}\&\mathrm{E}\mathrm{should}\mathrm{be}\mathrm{used}\mathrm{for}\mathrm{making}\mathrm{electric}\mathrm{wires}\mathrm{because}\mathrm{these}\mathrm{two}\mathrm{have}\mathrm{low}\mathrm{resistivity}. \end{gathered}$$