Physics

1. in the Atmosphere
©2008 Norm Ivey
Heat Transfer

2. What is Heat Transfer?
• Heat transfer is the movement of heat
energy from one substance to another.

3. • Heat (energy) always moves from a warmer
substance to a cooler substance.
Hot
Cold
What is Heat Transfer?

4. • Heat will continue to move until both
substances are the same temperature.
Hot
Cold Warm
Warm
What is Heat Transfer?

5. • The greater the difference in
temperature between the substances,
the faster the heat will transfer.
What is Heat Transfer?

6. • There are three types of heat transfer:
– Conduction
– Convection
– Radiation
What is Heat Transfer?

7. Examples
• You touch a black
car in the summer
and the heat from
the car transfers into
your hand.
• A breeze makes you
feel cooler because
the wind transfers
heat away from your
body.
• You feel the cold of a
winter day because
the cold air transfers
into you.
• Your Coke in a cooler
gets cold because the
cold from the ice
moves into the Coke.
Anti-Examples

8. Conduction
• Heat transfer by conduction is the
transfer of heat through direct contact.

9. Conduction
• Molecules transfer energy to the
molecules next to them.

10. Conduction
• The molecules
do not have to
be the same
substance.
http://www.theelusivefish.com/articles/wp-content/uploads/2007/09/hot-stove.jpg

11. Example 1
http://www.vernier.com/caliper/fall07/images/heat_transfer_large.jpg
The metal conducts heat from the cup
of warm water to the cup of cool water.

12. Your Coke becomes cold because the heat from the soda
transfers into the ice, not the other way around.
http://www.photoanswers.co.uk/ImgGalleryTn/91/10191/2417_16333.jpg
Example 2

13. No matter what it feels like,
cold does not transfer into
your body.
What is really happening
here?
Why do you wear heavy
clothes when it’s cold
outside?
http://www.alaska-in-pictures.com/data/media/9/man-in-extreme-cold_355.jpg

14. Radiation
• Heat transfer by radiation is the transfer of
heat through electromagnetic waves.
http://www.nmsu.edu/~safety/images/fire_meaney.gif

15. Radiation
• There is no direct contact between the
substances.

16. http://www.blog.thesietch.org/wp-content/uploads/2007/04/earth.jpg
http://stardate.org/images/gallery/sun5.jpg
Heat from the sun radiates through
empty space to earth.
Example 1

17. http://www.lifefamilytraining.com/img/roasting-marshmallows.jpg
Example 2
The heat from the campfire transfers
into your marshmallow, giving you a yummy, gooey treat!
(Direct contact between the fire and your marshmallow will ruin it!)

18. Convection
• Heat transfer by convection is the
transfer of heat through the fluid
(liquids and gases) movement of
currents.

19. Convection
• Warm fluids rise, cool down, sink, and
then are warmed again.

20. http://www.eeb.ucla.edu/test/faculty/nezlin/Lecture1/Fig0803.jpg
The radiator warms the room by warming the
air around it. Then the warm air transfers heat
to the rest of the room through convection.

21. http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap07/FG07_03.jpg
As air above the road warms up, it rises and is replaced by
cooler air, forming a convection current.

22. http://www.aos.wisc.edu/~aalopez/aos101/wk5/heatrans.jpg
This picture illustrates all three type of heat transfer.
Can you identify them all?
Conduction
Radiation
Convection