A house builder claims that replacing metal doorknobs and polished marble flooring with wooden doorknobs and thick woollen carpets will make a living room feel warmer in winter, even though the air temperature in the room is unchanged.
Explain this claim on the basis of thermal conductivity by answering the following parts.
(i) Define thermal conductivity and state its SI unit.
(ii) Using the concept of heat flow through the skin, explain why a metal doorknob feels colder to the hand than a wooden one when both are at the same room temperature.
(iii) A polished marble floor and a woollen carpet placed on it are both at 25∘C. Explain why bare feet sense the floor as cold and the carpet as warm.