# Video: Defining Thermal Conduction

Which of the following is the correct definition of conduction? [A] Conduction is the process of high-energy particles moving away from a part of a material that is hotter to one that is colder. [B] Conduction is the process of energy transferring from a hot object via the radiation of electromagnetic waves. [C] Conduction is the process of heat transferring from one part of the solid to another due to collisions between particles within the solid. [D] Conduction is the process of high-energy particles moving away from a part of a material that is colder to one that is hotter.

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### Video Transcript

Which of the following is the correct definition of conduction?

Now, we’ve been given four different definitions to go through. So let’s go through them one by one and see which one sounds right. As we’ll see in a second, this question will not only test our understanding of conduction, but also of the two other main heat transfer processes. So let’s go through statement number one and see if it’s the definition of conduction.

Conduction is the process of high-energy particles moving away from a part of a material that is hotter to one that is colder.

So here, we’ve got high-energy particles. And the particles themselves are moving away from a hot part of a material to a cold part. This is not the correct definition of conduction. In fact, this sounds more like convection. In convection, the heat transfer process occurs due to particles themselves moving from a hot place to a cold place. This happens because the particles originally in the hot place have more energy. Therefore, they’re moving about a lot more and end up moving towards the cold parts of the material. So no, this statement is not the correct definition of conduction. In fact, what we should do is replace the first word with convection. And then we can move on to statement number two.

Conduction is the process of energy transferring from a hot object via the radiation of electromagnetic waves.

Well, this again is not the definition of conduction. This is the definition of radiation. The clue’s in the statement. We’ve got: radiation of electromagnetic waves. One of the ways of transferring energy from a hot place is by radiation of electromagnetic waves. Most commonly, this emission is in the form of infrared radiation. So a hot object will emit infrared rays. And these rays will be carrying energy away from the object. Therefore, the object ends up cooling down. But again, this is not the definition of conduction. As we said earlier, this is radiation. So this one is not our answer either.

So number three: Conduction is the process of heat transferring from one part of the solid to another due to collisions between particles within the solid.

Now this sounds more like it. Conduction is a process which involves the particles in a solid. However, it’s not the transfer of the particles themselves that results in the transfer of energy. Instead, what we’ve got, is high-energy particles in one part of the solid, because we’ve maybe heated up that region, and lower energy particles in the colder part of the solid. Now what happens is, the particles in the hot part of the solid have more energy. Therefore, they vibrate more. They jiggle about all over the place, right? All of these particles are moving around. But what happens then is that they end up bumping into the particles from the cold part of the solid. And these collisions result in the colder particles also starting to jiggle about. So now we’ve got the colder particle starting to jiggle about a bit more. That way, we’ve got heat transfer from the hot part of the solid to the cold part of the solid without the particles actually going anywhere. All the particles do is jiggle about in roughly the same area. However, because they bump into each other, this results in a transfer of energy. This is slightly different from convection because earlier we said that conviction is when the hot particles themselves move to the cold part of the solid. So yes, this one does look like the right definition. However, let’s go through number four, just to make sure.

Conduction is the process of high-energy particles moving away from a part of a material that is colder to one that is hotter.

Well, this makes absolutely no sense. High-energy particles are concentrated in the hot part of the solid not in the cold part. So how are high-energy particles gonna be moving from the cold part of the solid to the hot part? So this statement isn’t even a definition of a heat transfer process. It just doesn’t make sense. Therefore, this one’s not our definition either. And we can happily say that number three is our final answer.

The definition of conduction therefore, is that conduction is the process of heat transferring from one part of the solid to another due to collisions between particles within the solid.