Rate of Heat Transfer Flashcards
What can different objects do?
Lose or gain heat much faster than other objects, even in the same conditions.
Where is heat radiated from?
The surface of an object.
The bigger the surface of an object means what?
More infrared radiation can be emitted from the surface, so quicker heat transfer.
Give an example of something which transfers heat?
Radiators.
They have large surface areas to maximise the amount of heat they transfer.
What do cars and motorbike engines often have>
Fins.
What do fins do?
They increase the surface area so heat is radiated away quicker.
Engine cools quicker.
What are heat sinks?
They are designed to transfer heat away from objects they are in contact with.
What do computer components have?
Fins and a large surface area so they can emit heat as quickly as possible.
What happens if 2 objects at the same TEMPERATURE and have the same SURFACE AREA but are at different VOLUMES?
The object with the smaller volume will cool more quickly .
Why will objects with small volumes cool much quicker?
As a high proportion of the object will be in contact with its surroundings.
What other factors affects heat energy transfer?
The material of the object.
What do objects made from good conductors do?
Transfer heat away more quickly compared to insulating materials.
If an object is in CONTACT with a conductor what will happen?
The heat will be conducted away much faster than if it is in contact with a insulator.
What are some devices designed to do?
Limit heat transfer.
What is a vacuum flask made up of?
Glass bottle.
Double-walled with a vacuum between the 2 walls.
What does the double-walls mean on a vacuum flask mean?
Stops conduction and convection through the sides.
What are the walls either side of the vacuum?
They are silvered to keep heat loss by radiation to a minimum.
The vacuum flask is supported by what?
Insulating foam.
The insulating foam in a vacuum flask does what?
It minimises heat conduction to or from the outer glass part.
What is the stopper in a vacuum flask made up off?
Plastic filled with cork or foam to reduce any heat conduction.
Humans and animals have what?
Ways of controlling heat transfer.
In the cold, why do our hairs stick up?
To trap a thicker layer of insulating air around the body.
The hair limits what?
Heat loss by convection.
What happens when you are too warm?
Your body diverts more blood flow near the surface of the skin so more heat can be lost as radiation.
