effects and transfer of heat

Question 1

define the conduction of heat

Answer 1

conduction is the transfer to heat through a medium without any flow of the medium

Question 2

how is a convection current set up?

Answer 2

the water at the bottom of the kettle nearest the heating coil is heated and expands. The expanded water is less dense than its surrounding water and rises. The water in the upper region of the kettle is cooler and denser and thus sinks to the bottom of the kettle to be heated by the heating coil. The difference in densities at different regions of the kettle sets up a convection current.

Question 3

why is the cooling tube of the fridge painted black?

Answer 3

Black is a good emitter of infrared radiation. hence, heat from the refrigerator will be lost to the surroundings at a faster rate