The electrical resistivities of four materials P, Q, R and S are given below:

P 6.84 × 10⁻⁸ Ωm

Q 1.70 × 10⁻⁸ Ωm

R 1.0 × 10¹⁵ Ωm

S 11.0 × 10⁻⁷ Ωm

Which material will you use for making: (a) heating element of electric iron (b) connecting wires of electric iron (c) covering of connecting wires? Give reason for your choice in each case.

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Solution

(a) Material S will be used for making the heating element of an electric iron as it has a high resistivity .
(b) Material Q will be used for making the connecting wires of an electric iron as it has a low resistivity.
(c) Material R will be used for making the covering of the connecting wires as it has an extremely high resistivity.

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P		2.3 × 10³ Ω m
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P		6.84 × 10⁻⁸ Ωm
Q		1.70 × 10⁻⁸ Ωm
R		1.0 × 10¹⁵ Ωm
S		11.0 × 10⁻⁷ Ωm