Question

The vacuum kept in between the walls of a thermos flask reduces the heat transfer by

• A. radiation only
• B. conduction only
• C. convection only
• D. conduction and convection.

Answer 1

The correct option is D conduction and convection.

The air gap between the two flasks is partially evacuated, resulting in a near vacuum that reduces heat transfer by conduction and convection significantly.
Hence, option (d) ‘Conduction and convection’ is correct.