Heat Transfer
Heat Transfer - Popcorn Lab | |
File Size: | 63 kb |
File Type: | docx |
Question: Which Direction does heat flow?
Does heat flow from hot to cold things or from cold to hot things? Or, does it flow both ways?
When I ask this very question to my students, most all of them invariably say both ways. It is then that I share the following story.
A very wealthy man was walking the streets of Downtown Provo - when he happens to come by a poor homeless man. Feeling compassion to the other fellow - he gives the homeless man some money to help him out.
Question: Which direction did the money flow? It's obvious that the money flowed from the rich man to the poor man - much like heat travels from something that is hot to something that is cold.
The poor man didn't give the rich man his poorness - much like the cold object didn't give the other object its coldness.
Poor and Cold are relative terms. In fact, I'd even dare say that there really isn't such a thing as cold - but rather something that lacks heat.
The reason why your hand feels warm when you touch a hot cup of Coco is because it's giving its heat to your hand. When you touch an Ice-cube, it's not giving you its coldness - but rather sucking out the heat from your hand. That's why your hand feels cold - you lack the heat that you once had - much like the rich man gave of his riches - now has less money.
A very wealthy man was walking the streets of Downtown Provo - when he happens to come by a poor homeless man. Feeling compassion to the other fellow - he gives the homeless man some money to help him out.
Question: Which direction did the money flow? It's obvious that the money flowed from the rich man to the poor man - much like heat travels from something that is hot to something that is cold.
The poor man didn't give the rich man his poorness - much like the cold object didn't give the other object its coldness.
Poor and Cold are relative terms. In fact, I'd even dare say that there really isn't such a thing as cold - but rather something that lacks heat.
The reason why your hand feels warm when you touch a hot cup of Coco is because it's giving its heat to your hand. When you touch an Ice-cube, it's not giving you its coldness - but rather sucking out the heat from your hand. That's why your hand feels cold - you lack the heat that you once had - much like the rich man gave of his riches - now has less money.
Three modes of heat transfer:
There are many ways to transfer money - cash, check, credit card - to name a few. There are only three ways to transfer heat.
The three ways for heat to transfer:
The three ways for heat to transfer:
- Conduction
- Convection
- Radiation
Conduction
Conduction is heat transfer from TOUCH.
As the atoms from the heat source heat up - they vibrate very fast. When something touches it, the atoms of the other object begin to bounce around as well when the atoms from the heat source collide with them. That is how heat is transferred through conduction. In this example, the stove is very hot. The heat is transferred to the Jiffy Pop container when the container touches the hot stove. |
Convection
Radiation
Radiation is heat transfer through LIGHT.
Microwaves are a type of light. Microwaves in particular, interacts with water molecules to get them excited and moving. That motion is what turns light energy into heat. This process is called radiation. Below is a more detailed version on how microwave ovens work. |
Three modes of heat transfer website.
Bill Nye - Heat
Bill Nye Video on Heat Transfer