Heat Transfer

Heat Transfer

Heat flows from HOT to COLD. The bigger the temperature difference, the more heat moves.

BUT the heat needs a ride--either conduction through a solid (or unmoving fluid), convection through a moving gas or liquid, or radiation using visible or invisible light.

Multiple Choice

In heat transfer, heat always flows from the _______________ substance to the _______________ substance.

• hotter to colder

• colder to hotter

• hotter to hotter

• colder to colder

Conduction

• Heat transferred in a solid or between two things that are touching.

• Good conductors like METAL move a lot of heat quickly, like a cooking pot or a cold lamp post.

• Things that DON'T transfer heat quickly are called insulators. It can be hot on one side of an insulator and cold on the other side without too much heat transferring.

• Your coat is a good example of an insulator.

Multiple Choice

Which is an example of heat being transferred by conduction?

• a furnace blowing hot air through vents

• an ice cube melting in a person’s hand

• boiling water transferring heat to noodles

• the sun heating water in a swimming pool

Multiple Choice

Which direction will the heat flow while this person holds a hot cup of tea?

• from the cup to her hand
• from her hand to the cup
• no heat is transferred

Multiple Choice

If I want two things to stay different temperatures from each other, I need to:

• Maximize heat Transfer

• Minimize heat transfer

• Make them touch a lot

• Blow on both with a fan

Convection

• Moving Air, or another liquid or gas can move lots of heat with it.

• A fan or pump can FORCE convection

• But warm air rises, so even with no fan, air will move given the chance.

• Cold air sinks--thats why those open freezers at the grocery store do OK with no lid.

Multiple Choice

Near the ceiling of a room the air is warmer. The warm air rises because of ________.

• conduction

• convection

• radiation

Multiple Choice

Which best describes the process of convection?

• Convection is the primary way  heat travels  through rays.
• Convection is the primary way heat travels  through metals.
• Convection is the primary way heat travels  through appliances.
• Convection is the primary way heat travels  through liquids and gasses.

Radiation

• EVERYTHING is glowing

• Humans emit Infrared light

• Hotter things (600 c) glow red and radiate more

• 900 c things glow orange, and radiate a ton.

• 1200 c things glow WHITE

• Past that you start to get more UV light.

Multiple Choice

When I emit (send out) IR radiation, my body gets:

• Hotter

• Cooler

• Stays the Same

• Humans don't emit radiation

Multiple Choice

The heat transferred from the Sun to the Earth by waves is called ________.

• conduction

• radiation

• convection

Multiple Choice

The baby chickens kept warm by the heat lamps. This is an example of ________.

• conduction

• convection

• radiation

Multiple Choice

The heat transferred from the Sun to the Earth by waves is called ________.

• conduction

• radiation

• convection