It is hotter for the same distance over the top of fire than it is inside of it, mainly because

(1) Air conducts heat upwards

(2) Heat is radiated upwards

(3) Convection takes more heat upwards

(4) Convection, conduction and radiation all contribute significantly transferring heat upwards

Air is a bad conductor of heat or partly conducts heat. Still, a vacuum is to be placed between the walls of the thermos flask because:

While measuring the thermal conductivity of a liquid, we keep the upper part hot and the lower part cool, so that:

Mode of transmission of heat, in which heat is carried by the moving particles, is 
(1) Radiation           

(2) Conduction

(3) Convection         

(4) Wave motion

In heat transfer, which method is based on gravitation ?

(1) Natural convection               

(2) Conduction

(3) Radiation                             

(4) Stirring of liquids