Thermos Flask and Heat Transfer
Thermos flasks are designed to prevent the transfer of heat through conduction, convection, and radiation. Let's delve into how they achieve this:

Conduction
- The inner chamber of a thermos flask is typically made of glass or metal, both of which are poor conductors of heat. This prevents heat from being transferred from the contents of the flask to the outside environment or vice versa.
- Additionally, there is a vacuum seal between the inner and outer walls of the flask, which further minimizes heat transfer by conduction.

Convection
- The vacuum seal in a thermos flask also inhibits heat transfer by convection. Convection relies on the movement of fluids (such as air or water) to transfer heat, but the vacuum eliminates any air or other gases that could carry heat away.

Radiation
- The reflective surfaces on the inner walls of a thermos flask help to prevent heat transfer by radiation. These surfaces reflect heat back towards the contents of the flask, rather than allowing it to escape.
- Additionally, the vacuum seal acts as a barrier to radiation, as there is no medium (such as air) through which heat can be radiated.
In conclusion, a thermos flask effectively prevents the transfer of heat through conduction, convection, and radiation by utilizing materials with low thermal conductivity, creating a vacuum seal to eliminate air and gases, and incorporating reflective surfaces to reflect heat back towards the contents of the flask.