WHAT IS HEAT AND HOW DOES IT TRAVEL
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On the previous lesson, we learnt that thermal energy is produced by the movement of the particles that make up objects. If the particles move slow, that object will be cold. If the particles move quick, that object will be hot. We also studied that we can change the temperature of an object: if we add energy, the object will get hotter; and if we take away energy, the object will get colder.
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But, how can thermal energy travel? To answer that question, first we have to learn that there are two types of objects according to how they transfer thermal energy: conductors and insulators.
CONDUCTORS: they transfer thermal energy very easily. Metal is a good example of thermal conductor.
INSULATORS: they transfer thermal energy badly. wood and paper are examples of thermal insulators.
In the following picture, the copper is the conductor and the plastic is the insulator.
CONDUCTORS: they transfer thermal energy very easily. Metal is a good example of thermal conductor.
INSULATORS: they transfer thermal energy badly. wood and paper are examples of thermal insulators.
In the following picture, the copper is the conductor and the plastic is the insulator.
After learning that there are thermal conductors and thermal insulators, we have to learn the mechanisms to transfer thermal energy from one object to another.
There are 3 mechanisms: conduction, convection and radiation.
CONDUCTION
Conduction is the transfer of thermal energy between two objects that are in contact. Let's see how it works:
There are 3 mechanisms: conduction, convection and radiation.
CONDUCTION
Conduction is the transfer of thermal energy between two objects that are in contact. Let's see how it works:
- The particles in the hotter object are moving fast, and the particles in the colder object are moving slow.
- The particles that are in contact in both objects start to interact: the faster particles transfer energy to the slower particles.
- So, the particles in the colder object start moving faster and that object get hotter.
- The first object losses some energy, so it will get colder.
CONVECTION
Convection only occurs in a liquid or a gas. How does it work?
Convection only occurs in a liquid or a gas. How does it work?
- The water at the bottom of the pot is heated by conduction, so the particles start moving faster than the rest of the particles.
- The faster particles, the hotter ones, start moving up; while the slower particles, the colder ones, start moving down. That creates a circular movement.
- Thanks to that circular movement, all the particles get hot.
RADIATION
Objects can transmit thermal energy in the form of electromagnetic waves. That is what we call radiation. A good example is the Sun: the thermal energy from the Sun is transferred to the Earth by radiation.
Objects can transmit thermal energy in the form of electromagnetic waves. That is what we call radiation. A good example is the Sun: the thermal energy from the Sun is transferred to the Earth by radiation.
Let's see how do conduction, convection and radiation work on the following animation (click on the picture).
Do you like singing? So try this song about heat transfer.
What about playing some games to make things easier? Go to the games section.