Conduction and Convection

Let's do an experiment with a candle and an aluminium rod.

Take the aluminium rod and uniformly stick some nails using candle wax on it as shown

Now let's heat the aluminium rod at one end with a candle, and see what happens.

The nail nearest to the candle falls first, then the latter.

Here the heat is first coming from the candle towards nail C and melts the wax. So it falls. Later the heat goes to nail B and does the same.

This type of transfer of heat from one place to another in materials is called conduction.

You can see conduction in a hot frying pan, with no handle. The heat flows from pan to handle and when you touch it it will be very hot.

Let's do another activity.

If the water in the figure is hot, then the spoon will be hotter than the plastic scale and wooden pencil.

This is because conduction is better in a few elements like metals. It is very less in plastic and wooden materials.

The materials that conduct heat are called thermal conductors. The materials that don't conduct heat are called thermal insulators.

The important point to remember in conduction is that heat travels from one point to other through the material.

Even though the heat is passing through the material, there is no movement in the material.

Now let's look at another example of bonfire.

Even though there is a distance between fire and us, we can feel hot air on our face. This type of heat transfer is called CONVECTION.

Now let's learn what convection is.

In convection, the air around the fire gets heated and moves very fast.

This heated air moves away from the fire and cool air flows towards the fire, this creates a hot airflow.

We experience hot airflow in summer due to convection.

Same this happens in case of land and sea breeze. In the day, Land is hotter than the sea so warm air goes from land to sea and cool air goes from sea to land.

At night the land is cooler than the sea, so the cool air goes from land to sea and the warm air goes from sea to land. The people who live in coastal areas experience this.

Land and sea breeze occur due to convection.

Now let's understand the difference between conduction and convection.

In conduction while transferring heat, there is no actual movement of particles. In convection, there is a movement of the particles.

Revision

Heat has a property of flowing from one place to another. One way is conduction and another is convection.

In conduction, heat is flowing from one place to another through materials without any actual movement of the material. eg: conduction in metals.

In convection, heat is flowing from one place to another by the flow of air or water or any fluid. Eg: boiling water, hot air in summer.

The End