P1 - Infrared Flashcards
Why is it best to paint the outside of a metal cooking pot black?
Because black is a good absorber of heat. The heat will be used to cook the food.
Why does a cooking pot have a lid?
To reduce energy loss by convection.
Why is a car radiator painted black?
Black is a good emitter of heat, the heat is emitted to the surroundings to keep the engine cool.
Explain why thermal imaging cameras work better at night than during the day.
At night the surroundings are cooler so the surroundings emit less IR radiation than the warm body and this gives a clearer image.
What is the name given to heat transfer from particle to particle?
Conduction
What name is given to the heat transfer by the movement of hot liquids?
Convection
Why is the outside of a fire fighter’s suit shiny?
To reflect heat away from the fire fighter.
How is heat transferred through a metal?
Free electrons inside the metal gain kinetic energy and collide with the metal ions.
Why are radiators painted white and not black?
if they were painted black, they would transfer heat too quickly and the watertemperature inside theradiator would drop too quickly. The next radiator would then stay cold.
How does the Sun transfer heat?
Radiation
A bag is filled with water and placed in the Sun. What colour should the bag be so that the water can be warmed?
Black, as black surfaces are good absorbers and emitters of thermal energy. Heat from theSun is absorbed and used to heat the water.
Which methods of heat transfer are reduced by a vacuum?
Convection and conduction as both require particles.
which method of heat transfer is reduced by silver surfaces?
Radiation; heat is reflected
Which methods of heat transfer are reduced by plastic caps?
conduction as plastics are good insulators & convection
Why does a fridge have a white shiny surface?
A white shiny Surface is a poor absorber of heat and reduces heat transfer into the fridge. The heat is reflected instead.
