Fundamentals of Heat Transfer (Conduction, Convection & Radiation) | फंडामेंटल्स ऑफ़ हीट ट्रांसफर |

Fundamentals of Heat Transfer (Conduction, Convection & Radiation) | फंडामेंटल्स ऑफ़ हीट ट्रांसफर |
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What is Temperature?
The temperature of a body is the measure of the amount of heat content possessed by it. It is measured in degree Celsius (°C) or Kelvin(°K). The temperature of a substance is a physical quantity that measures the degree of hotness or coldness of a body.

Thermal Properties of Matter
The properties of the matter involving heat transfer and measurement are known as ‘Thermal Properties of Matter’

Heat Transfer
Heat energy can be transferred from one body to the other or from one location in a body to the other. Study of the techniques and methods adopted to transfer heat energy is known as ‘Heat Transfer’. To facilitate heat transfer between 2 bodies there needs to be a temperature difference between them.This means that these bodies must be a 2 different temperatures one higher than the other to allow heat to flow from one body to the other.

This means that no heat transfer occurs between 2 bodies which are at the same temperature. At the same time, it is very important to note that heat only flows from a body at higher temperature to a body at a lower temperature. Although this may look obvious, this law is very important from the point of view of thermodynamics.
Heat transfer takes place in 1 of the three ways namely: Conduction, Convection and Radiation We will discuss each of these methods in detail.

Conduction
Conduction is the method of transfer of heat within a body or from one body to the other due to the transfer of heat by molecules vibrating at their mean positions. The bodies through which the heat transfer must be in contact with each other. There is no actual movement of matter while transferring heat from one location to the other.

Conduction occurs usually in solids where molecules in the structure are held together strongly by inter molecular forces of attraction amongst them and so they only vibrate about their mean positions as they receive heat energy and thus pass it to the surrounding molecules by vibrations.

Convection
Convection is the mode of heat transfer which occurs mostly in liquids and gases.In this method, heat transfer takes place with the actual motion of matter from one place within the body to the other. Often when we boil water we have seen bubbles and currents develop in the water on careful observation.

This is an apt example of the convection process. The hot water at the bottom becomes lighter and moves upwards forcing the cold and denser water at the top to come down and thus get heated up.
Radiation
Radiation is another form of heat transfer. It does not require any medium and can be used for transfer of heat in a vacuum as well. This method uses electromagnetic waves which transfer heat from one place to the other. The heat and light from the sun in our solar system reach our planet using radiation only.

In fact, radiation is the most potent method of heat transfer. In winters when we sit near a fire we feel warm without actually touching the burning wood. This is possible by radiation only.
Newton’s Law of cooling
Newton’s law of Cooling states that there is always a direct correlation between the rate of change of temperature of a body and the temperature difference between the object and the surroundings. What this simply means is a hot body will cool down faster if the temperature of the body is much greater than that of the ambient. Whereas another body which has a temperature that is closer to the ambient temperature will take a little more time.

For example, A cup of tea at 80° Celsius loses heat at a much faster rate to a surrounding at a temperature of 25°Celsius as compared to a cup of tea which is at 35° Celcius. This brings us to the end of our discussion. A thorough knowledge of these concepts will go a long way to help the reader understand concepts of heat transfers, thermodynamics, and their applications as well.
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Видео Fundamentals of Heat Transfer (Conduction, Convection & Radiation) | फंडामेंटल्स ऑफ़ हीट ट्रांसफर | канала Toppr Class 8-10