Question

explain how thermos flask minimises loss of heat by conduction , convection and radiation

Answer 1

Function of the thermos flask is to prevent the flow of heat to and from the bottle. We know that heat can flow from one place to another by three processes: conduction, convection and radiation. The thermos flask prevents the flow of heat by any of these processes. The flask is made up of glass which is a bad conductor of heat. Hence heat does not flow by conduction. Since there is vacuum between the walls of the bottle, flow of heat by convection is also ruled out. Due to the silvering of the walls heat is not lost by radiation. As a result, hot things kept in a thermos flask, do not become cold and cold ones do not become hot for a long time.

Answer 2

Continuous

finally as the inner wall of glass bottle are silvered , any heat that may be radiated is reflected back into the flask