Transcript Heat Transfer PowerPoint

Heat Transfer
Convection, Conduction,
and Radiation
On a chilly night, we gather around a campfire
to warm our hands and feet.
How is heat transferred in this example?
Radiation
Why would getting warm by a campfire be an
example of radiation?
• The transfer of electromagnetic waves occurs
at a distance through the air between the fire
and the person sitting near it.
• When the electromagnetic waves come in
contact with an object, waves transfer heat to
the object.
Fire heats the air inside a hot air balloon. Then
the balloon rises high into the sky.
How is heat transferred in this example?
Convection
Why would a hot air balloon rising be an
example of convection?
• Convection is the up and down movement of
gases and liquids caused by heat transfer.
• Air is a mixture of gases.
• As gases are heated, they warm, expand, and
rise.
I am going to heat up my leftovers in the
microwave.
How is heat transferred in this example?
Radiation
Why would heating food in a microwave oven be
an example of radiation?
• The transfer of electromagnetic waves occurs
at a distance through air inside the microwave
oven.
• When the electromagnetic waves come in
contact with food, waves transfer heat to the
food.
An electric blanket will make my bed cozy and
warm on long winter nights.
How is heat transferred in this example?
Conduction
Why would placing an electric blanket on a bed
be an example of conduction?
• The electric blanket is in direct contact with
the bed.
• Heat is transferred because the objects are
touching.
Brrr! The first floor of the apartment building
feels cooler than the upper floors.
How is heat transferred in this example?
Convection
Why would lower floors of an apartment
building feeling cool be an example of
convection?
• Convection is the up and down movement of
gases and liquids caused by heat transfer.
• Air is a mixture of gases.
• As gases are heated, they warm, expand, and
rise.
While visiting the beach, the sea breeze blows
across my face.
How is heat transferred in this example?
Convection
Why would a sea breeze at the beach be an
example of convection?
• Convection is the up and down movement of
gases and liquids caused by heat transfer.
• Air is a mixture of gases.
• As gases are heated, they warm, expand, and
rise.
Be careful when picking up that cup of coffee.
It’s hot!
How is heat transferred in this example?
Conduction
Why would picking up a cup of hot coffee be an
example of conduction?
• The hot coffee is in direct contact with the
cup.
• When the cup is picked up, it will be in direct
contact with your hand.
• Heat is transferred through objects that are
touching.
That lamp has been on for a while because it
feels warm when I put my hand near the light
bulb.
How is heat transferred in this example?
Radiation
Why would a warm light bulb be an example of
radiation?
• The transfer of electromagnetic waves occurs
at a distance through air between the light
bulb and your hand.
• When the electromagnetic waves come in
contact with your hand, waves transfer heat to
it.
You should use sunscreen lotion at the beach to
avoid getting a nasty sunburn.
How is heat transferred in this example?
Radiation
Why would getting a sunburn be an example of
radiation?
• The transfer of electromagnetic waves occurs
at a distance through space and air between
the Sun and your skin.
• When the electromagnetic waves come in
contact with your skin, waves transfer heat to
it causing a possible sunburn.
The water in the lake felt warm, but as I swam
deeper, it felt cold.
How is heat transferred in this example?
Convection
Why would water feeling cooler deeper in the
lake be an example of convection?
• Convection is the up and down movement of
gases and liquids caused by heat transfer.
• Water is a liquid.
• As liquids are heated, they warm, expand, and
rise.
Ouch! I got burned when I touched the stove.
How is heat transferred in this example?
Conduction
Why would getting burned when touching a hot
stove be an example of conduction?
• Your hand is in direct contact with the stove.
• Heat is transferred through objects that are
touching.
I left a metal spoon in a pot of boiling water and
now the spoon is too hot to touch.
How is heat transferred in this example?
Conduction
Why would a metal spoon left in a pot of boiling
water be an example of conduction?
• Metal is a good conductor.
• The metal spoon is in direct contact with the
boiling water and pot.
• Heat is transferred through objects that are
touching.