Question

The thermos bottles have a highly polished interior made of stainless steel, which makes them almost unbreakable. These thermos bottles are also covered with insulated material to keep substances hot by reducing heat loss. Identify which of the following modes of heat transfer is restricted by the insulated material?
(A) Absorption
(B) Conduction
(C) Convection
(D) Radiation
(E) Evaporation

Answer 1

Hint: In order to solve this question, we are going to first explain how the material of which the thermos flask is made of, affects the transfer of the heat by any type of the heat transfer process. How the transfer of the heat is restricted due to the structure of the bottle and get the correct answer.

Complete answer:
A vacuum flask, or thermos doesn’t allow the heat transfer by these ways. Silver coating on the inner side prevents heat transfer by convection and the vacuum between its double wall prevents heat moving by convection. The thinness of the glass walls stop entering or leaving the flask by conduction.
Hence, only (D) radiation is possible.

Note:
The absorption is the process of taking up the energy so that the type of the energy present around becomes the internal energy of the absorber.
Conduction is the process of the transfer of internal energy by microscopic collisions of particles and movement of electrons within a body.
Convection is the process of transfer of heat due to the bulk movement of molecules of the fluids.
Radiation is the emission of the heat in the form of the waves of the particles.
Evaporation is formation of vapors that occurs on the surface of the liquids when they change to the gaseous phase.