The thermos flask is basically two flasks, one in side the other, in between the two flasks a vacuum is produced. Convection requires a liquid or a gas to transfer heat, therefore it can't happen in a vacuum.
There are many ways this is done. It can be done by having a double walled thermos with either air, an insulator, or a vacuum between. A vacuum will prevent all conduction except where the two walls...
There is a layer of vacuum which surrounds the flask, then the inside is covered by shiny material which will reflect the heat back into the flask, there are two lids, and there is an indirect gap of...
A vacuum between two glass sheets will greatly reduce heat loss through convection, and also through conduction. The fact that the glass is coated (to convert it to a mirror) also reduces the loss by...
It is nearly impossible to let a thermos flask lose heat to its surroundings because, space between the double walls of the thermos flask has been vacuumed, therefore heat has nothing to rely on to...
Thermos flask is a thermos container used to store liquids like any hot drink. The liquid added to thermos flask will retain the temperature even after some time irrespective of external temperatures.