Question

A thermos flask is designed to prevent the contents of the flask from losing heat. Which of the following statements concerning the design of thermos flasks is incorrect?

• A. The stopper helps reduce heat loss by convection
• B. The glass walls are silver coated to reduce emitted radiation
• C. The flask is designed to prevent heat loss by conduction, convection and radiation
• D. The vacuum between the glass walls prevents heat loss by preventing radiation

Answer 1

The correct option is D The vacuum between the glass walls prevents heat loss by preventing radiation

Yes, thermoflask is designed to prevent the contents of the flask from losing heat.

The stopper, i.e. vacuum between double walls of thermoflask prevents heat transfer through convection.

The glass walls are silver coated because it reduces emitted radiation when they are silver coated i.e. made shiny. And we know that shiny surfaces reflects all the heat so all the heat is being reflected inside the walls and heat remains unaffected. And the thinesss of glass walls will stop heat entering or leaving the flask by conduction.

So, the flask is designed to prevent heat loss by conduction, convection and radiation.