Question

In a thermos-flask, a warm substance remains warm because

• A. Transfer of heat has been minimised in it
• B. No heat either enters into nor leaves the inside of the thermos flask by any of the three methods of transmission conduction, convection and radiation
• C. Heat is constantly generated to maintain the temperature of the cooling substance
• D. Thermos flask is made of a material having the property of maintaining temperature at constant
• E. None of these

Answer 1

The correct option is A Transfer of heat has been minimised in it

A Thermos-flask retains the temperature of the liquid that is kept inside it. The basic principle of a flask is to insulate the substance from the outside air so that no heat transfer takes place. When there is no heat transfer the temperature of the substance remains the same.