In a thermo-flask, cork is placed between the evacuated inner cylinder and the outer jacket to reduce heat loss or gain due to ____________ process.
A. combustion B. convection C. radiation D. conduction
Correct Answer: B
Explanation
The thermo flask or vacuum flask keeps hot liquids hot and cold liquids cold for a long time. Heat is prevented from getting into or out of the flask by the following features: i. A double - walled silvered surface minimizing loss or gain of radiant heat to the outside ii. A vacuum between the walls reducing the loss or gain of heat by conduction and convection iii. An insulating support preventing heat loss or gain by conduction iv. An insulating stopper or cork preventing heat loss by evaporation and convection if the flask contains hot liquid and only convection if it contains cold liquid.
