10.5 Part 3 Applications of Thermal Energy Transfer (Radiation)

In the above picture, Cup 1 is made of metal painted black. It has no lid and no saucer. Cup 2 is made from white china. It has a lid and is resting on a cork mat. Both cups are the same size and both are filled with boiling water at the same time.

The water in Cup2 will remain hot for the longest time. It has a lid that stops convection currents as the air heated by the coffee cannot rise. The white, shiny surface of the cup does not radiate heat well. Cork is also a poor conductor of heat so heat cannot travel down into the table.








Cooling fins that is placed at the refrigerator

The cooling fins at the back of refrigerators are also painted black. However, these are used to radiate heat quickly to the surroundings.

Dark surfaces are good absorbers of heat. Solar panels are black to absorb more heat to heat up water.








Space suit

Space suits of astronauts are shiny so as not to absorb much radiated heat.

The inner surface of an electric oven is rough and painted dull black so that it is a good emitter of radiated heat.