talk about the topic heat it can still be confusing for some people. In thermology, heat is linked to the transfer of thermal energy from a higher-temperature body to a lower-temperature body, that is, heat is energy in transit. For better assimilation, let's go to the following example:
Let's imagine that, in an isolated system (inside a Styrofoam box, for example), two objects were placed. Object A, at a temperature of 200°C; and object B, at a temperature of 20°C. According to the zero law of thermodynamics, over time, the temperature of object A decreases while that the temperature of object B increases, until both reach the same temperature, remaining in equilibrium thermal. The energy that has been transferred from object A to object B is called heat or thermal energy.
Mind Map: Heat
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Heat Transmission
In order for heat to be exchanged, it must be transferred from one region to another through the body itself, or from one body to another. There are three heat transfer processes studied in thermology, they are: conduction, convection and irradiation. Irradiation is the propagation of electromagnetic waves that do not need a medium to propagate, while that conduction and convection are transfer processes that require a material medium to propagate.
Driving
When two bodies with different temperatures are brought into contact, the molecules of the hotter body, colliding with the molecules of the colder body, transfer energy to it. This heat conduction process is called conduction. In the case of metals, in addition to the transmission of energy from atom to atom, there is the transmission of energy by free electrons, that is, it is the electrons that are more away from the nucleus and which are more weakly bound to the nuclei, so these electrons, colliding with each other and with atoms, transfer energy quite a bit ease. For this reason, metal conducts heat more efficiently than other materials.
Convection
Like metal, liquids and gases are good conductors of heat. However, they transfer heat in a different way. This shape is called convection. This is a process that consists of moving parts of the fluid within the fluid itself. For example, let's consider a vessel that contains water at an initial temperature of 4°C. We know that water above 4ºC expands, so when we put this vessel over a flame, the part of beneath the water will expand, having its density diminished, and thus, according to Archimedes' Principle, will rise. The coldest and densest part will descend, then forming the convection currents. As an example of convection we have the refrigerator, which has its freezer on top. The cold air gets denser and goes down, the air below, warmer, goes up.
Irradiation
We can say that thermal irradiation is the most important process, as without it, life on Earth would be practically impossible. It is by radiation that the heat released by the Sun reaches the Earth. Another important factor is that all bodies emit radiation, that is, they emit waves electromagnetic, whose characteristics and intensity depend on the material of which the body is made and of your temperature. Therefore, the process of emitting electromagnetic waves is called irradiation. The thermos is a good example of thermal radiation. The inner part is a glass bottle with double walls, with almost a vacuum between them. This makes it difficult to transmit heat by conduction. The inside and outside of the bottle are mirrored to prevent radiant heat transmission.
By Domitiano Marques
Graduated in Physics
*Mind Map by Rafael Helerbrock
Master in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/processo-propagacao-calor.htm
