The electrical resistivities of four materials P,Q,R and S are given below:
`{:(P,,6.84 xx 10^(-8) Omegam),(Q,,1.70 xx 10^(-8) Omega m),(R,,1.0 xx 10^(15) Omega m),(S,,11.0 xx 10^(-7)Omega m):}`
Which material will you use for making: (a) heating element of electric iron (b) connecting wire of electric iron (c) covering of connecting wires? Give reason for your choice in each case.

Answer

(a) S;Because it has high resistivity of `11.0 xx 10^(-7) Omega m` (It is actually nichrome) (b) Q; Because it has very low resistivity of `1.70 xx 10^(-8) Omega m` (It is actually copper) (c) R; Because it has very, very high resistivity of `1.0 xx 10^(15) Omega m` (It is actually rubber)