Question

Which of the following statements are incorrect? Rewrite them correctly in your notebook.
(a) A Thermos flask that is used to store either cold or hot liquids for several hours minimises heat transfer by conduction and convection only.
(b) We receive heat from the sun by radiation.
(c) Dark objects are better absorbers and better radiators of heat.
(d) Air is a good conductor of heat.
(e) Solids expand more than liquids.
(f) Overhead telephone and electric wires are kept loose because it is difficult to stretch them.
(g) The silvered walls of a thermos flask prevent loss of heat by convection.

Answer 1

(a) False
A Thermos flask that is used to store either cold or hot liquids for several hours minimises heat transfer by conduction, convection and radiation processes.

(b) True

(c) True

(d) False
Air is a bad conductor of heat.

(e) False
Solids expand less than liquids.

(f) False
Overhead telephone and electric wires are kept loose because these wires contract when temperature decrease.

(g) False
The silvered walls of a Thermos flask prevent loss of heat by radiation.