The electrical resistivities of four materials P, Q, R and S are given below : P - 6.84 × 10 -8 Ω m Q - 1.70 × 10 -8 Ω m R - 1.0 × 10 15 Ω m S - 11.0 × 10 -7 Ω m 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.

Question

The electrical resistivities of four materials P, Q, R and S are given below : P - 6.84 &#xD7; 10 -8 &#x3A9; m Q - 1.70 &#xD7; 10 -8 &#x3A9; m R - 1.0 &#xD7; 10 15 &#x3A9; m S - 11.0 &#xD7; 10 -7 &#x3A9; m 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.

Philoid · Accepted Answer

(a) The metals and alloy have very low resistivity in the range of 10^-8 ohm meter to 10^-6 ohm meter, so they are good conductor of electricity. While insulators have resistivity of the order of 10¹² to 10¹⁷ ohm meter. Alloys have generally higher resistivity than its constituent metals and consider good for the heating elements. So S is used for heating element of electric iron.

(b) Q has very low resistivity of 1.7 X10^-8ohm-m (it is actually copper). So it is used in connecting wires of electric iron.

(c) R has very high resistivity of 1.0X10¹⁵ohm-m (it is actually rubber). So it is used for covering of connecting wires.