in the Atmosphere

Thermal Energy Transfer

• There are three types of thermal energy transfer:– Radiation– Conduction– Convection

What is Thermal Energy Transfer?

Radiation

• Heat transfer by radiation is the transfer of heat through electromagnetic waves.

http://www.nmsu.edu/~safety/images/fire_meaney.gif

Radiation

• There is no direct contact between the substances.

http://www.blog.thesietch.org/wp-content/uploads/2007/04/earth.jpghttp://stardate.org/images/gallery/sun5.jpg

Radiant Energy from the sun radiates through

empty space to earth.

Radiant Energy from the sun consists of :

1. Visible Light2. Ultraviolet Light- has a shorter wavelength

than visible light and can cause sunburn and skin cancer

3. Infrared Radiation- has longer wave length than visible light and is felt as heat

ENERGY ON EARTH

• Not all of the sun’s energy reaches the Earth’s Surface.

• 20% of the Sun’s Energy is ABSORBED by gases and particles in the Atmosphere.• Ozone, Oxygen & Water Vapor absorb ultraviolet

light• Water and carbon dioxide(CO2) absorb infrared

light.• Earth’s Atmosphere (clouds) and the surface of the

Earth REFLECTS about 30% of Sun’s radiation• About 50% of the Sun’s radiation is absorbed by the

Earth's Surface

RADIATION BALANCE

Land, trees, and the oceans absorb and emit solar radiation mainly in the form of infrared radiation.

Earth’s temperature remains stable because of the balance between the amount of radiation coming from the Sun and the amount going out from Earth.

THE GREENHOUSE EFFECT

Glass allows sunlight into a green house. It prevents infrared radiation from escaping which keeps the greenhouse warm

THE GREENHOUSE EFFECTCertain gases, such as CO2, in the atmosphere act like the glass in a greenhouse warming the atmosphere.

• Thermal energy transfer is the movement of heat energy from one substance to another.

• Heat (energy) always moves from objects with high temperature to objects with low

HotCold

What is Thermal Energy Transfer?

• Heat will continue to move until both substances are the same temperature.

WarmWarm

What is Thermal Energy Transfer?

• The greater the difference in temperature between the substances, the faster the heat will transfer.

What is Thermal Energy Transfer?

Your Coke becomes cold because the heat from the soda transfers into the ice, not the other way around.

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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

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

Conduction• The transfer of thermal energy by the

collisions between particles of matter. (through direct contact).

• Molecules transfer energy to the molecules next to them.

Conduction

• The molecules do not have to be the same substance.

http://www.theelusivefish.com/articles/wp-content/uploads/2007/09/hot-stove.jpg

Conduction

• Thermal energy is CONDUCTED from the warm ground to the air above it.

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As air above the road warms up, it becomes less dense and rises and is replaced by

cooler air, forming a convection current.

Convection

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

Convection

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

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The radiator warms the room by warming theair around it. Then the warm air transfers heat

to the rest of the room through convection.

When water changes from one phase to another, Latent heat is exchanged.

http://www.aos.wisc.edu/~aalopez/aos101/wk5/heatrans.jpg

This picture illustrates all three type of heat transfer.Can you identify them all?

http://www.aos.wisc.edu/~aalopez/aos101/wk5/heatrans.jpg

Conduction

Radiation

Convection