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HEAT SPREAD MEANS

The purpose of this report is to identify and classify forms of heat propagation, to conclude that heat, in order to propagate, requires a temperature difference between the flow regions, to conclude that the thermal flow always occurs in the sense of decreasing temperatures. To demonstrate the means of heat propagation, three experiments were carried out, being conduction, convection and irradiation. With the realization of the experiment it can be concluded that in the conduction process the energy transmission is made from molecule to molecule, but without the displacement of matter. In the convection process the transformation of thermal energy is made from molecule to molecule, with the displacement of matter. In irradiation the thermal energy emitted by the lamp causes the temperature to increase through the irradiation of electromagnetic waves.

introduction Heat, which can also be called thermal energy, corresponds to energy in transit that is transferred from one body to another due to the temperature difference. This transfer always occurs from the highest temperature body to the lowest temperature body until they reach the thermal equilibrium. The heat transfer takes place by three differentprocesses: conduction, convectionand irradiation. In conduction, heat energy is transmitted by means of solid bodies that heat up, either by heat from fire, or by contact with another warmer one. Thus, when we heat a solid body, the kinetic energy increases and consequently the agitation of the molecules also increases, thus causing heat to be driven throughout the material. We can take as an example the situation where if we leave a metal ember anaister on fire long enough, your cable will heat up. The energy is transferred from the fire to the cable by conducting along the understatement. The amplitudes of the vibrations of the atoms and electrons of the metal at the end of the tuna in contact with the fire become relatively intense because of the high temperature of the environment. These intensified vibration amplitudes, and therefore the associated energy, are transferred along the atom-to-atom atom in

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collisions between adjacent atoms. In this way, a region of increasing temperature is understood along the racer towards the cable. In the convection, heat transmission occurs in substances that are in the liquid or gaseous state. Circular currents are created called "convection currents", which are determined by the density difference between the hottest and the coldest fluid. When you look at the flame of a candle or a match, you are observing the thermal energy being transported upwardby convection. Such a transfer of energy occurs when a fluid, such as air or water, comes into contact with an object whose temperature is higher than that of the fluid. The temperature of the fluid part that is in touchwith the hot object increasesand this part of the fluid expands, becoming less dense. As this expanded fluid is now lighter than the fluid around, colder, buoyancy forces cause it to rise. The coldest fluid then flows to take the place of the hottest fluid that rises, and the process continues. In irradiation, transference of thermal energy occurs through electromagnetic waves or heat waves of abody. In this case, the electrical particles of an object increase, just like its kinetic energy. We can mention the exemplo of the Sun in relation to the Earth:thende the solar heat crosses the vacuum (there is no matter in space) and reaches the Earth through Irradiation.

Experimental procedure To prove the heat transfer laws, three experiments were carried out in order to observe the types of heat propagation medium. In the first experiment, the following equipment was used: A tripod; five small spheres; a lamp; ruler; candle and phosphorus. The equipment was assembled according to Figure I.

stopwatch, a thermometer table holder and a thermometer. Figure III shows the necessary materials and their assembly form.

Figure III: thermal source of the heat propagation set, with the other equipment (irradiation).

Figure I: Equipment used in the first experiment (conduction).

Initially, the trough A of figure I was raised to 2 cm from the lamp, the candle was lit with the match and at the same time that the parafines of the candle were dripped in the trough, the spheres were positioned in sequence. Soon after, the lighted lamp was placed below the gutter and timed the time when the spheres took to fall. See table I. Table I: Time of fall between the balls in the gutter. sphere 1-2 2-3 3-4 4-5 Time(s) 9,3 10,6 12,3 12,9

In the second experiment, a demonstration set of heat propagation and a fan was required, assembled according to Figure II.

Figure II: Heat propagation statement set with a fan (convection).

In this experiment, after turning on the heat statement set, the time was timed when the fan reached a uniform constant velocity of 75 s. Finally, in the third experiment we used a thermal source of the heat propagation set, a sulfite leaf, a carbon sheet, ruler, a

The thermometer was placed a distance of 20cm from the thermal source, and timed 5 minutes to evaluate the final temperature of the stopwatch. This procedure was repeated two more times, once with the sulfite leaf in front and another withcarbon, and each time the thermometer was cooled to 23ºC. The temperature data can be found in Table III. Table III: temperature marked on the thermometer directly on the beam of light, with sulfite paper and carbon paper. Tue = 23ºC bluntly Sulfite carbon temperature

26°C

27°C

29°C

Results and discussion With the experiment, it was possible to analyze the means of heat propagation by the methods of conduction, convection and irradiation. Propagation by conduction requires contact between objects that will exchange heat, that is, it occurs when molecules and atoms of an object at a high temperature transmit thermal energy to nearby molecules or atoms with low energy. Therefore, we observed the heat transfer by conduction at the moment when the trough warmed and the paraffin melted, letting the spheres fall sequentially. Subsequently, it was possible to analyze the heat propagation movement, by convection basedon the principle of Archimedes. Based on the theory, it was possible to analyze in the experiment that after the lamp was accessed for a few seconds, it began to

rotate the helix, because the cold air molecules are denser and were close to the

heated lamp, however, the heat of the lamp warmed the air causing the cold air to descend, occupying the space of the hot air molecules that are less dense and causing them to rise. Thus forming, convection currents or heat exchange. Finally, it was possible to analyze the irradiation movement. In thismovement, thermal energy crosses space, including the vacuum inside the lamp until it reaches the thermometer bulb. In addition, these infrared irradiations of an electromagnetic nature do not require a means to propagate. In the experiment in question, the thermal energy emitted by the lamp caused the temperature indicated in the thermometer to increase through the irradiation of electromagnetic waves. Two tests were performed using initially a sheet of sulfite paper positioned in front of the thermometer and later a carbon sheet of paper. With this, it was possible to analyze that with carbon paper the temperature of the thermometer increased more than normal (without paper), since the dark color of the paper causes more heat to be absorbed and consequently increases the temperature of the thermometer. Conclusions Through the conduction experiment, it was possible to observe that the conduction of fire by transferring heat to the trough caused the transfer of energy from molecule to molecule successively throughout the end, where sequential fall of the spheres trapped by paraffin occurs. In the convection method, it was observed that after the lamp was lit for a few seconds, the propeller began to rotate, as the air molecules rise and the cold air molecules descend because they are denser. And in the latter, in the irradiation method it was noticed that the thermal energy of the lamp caused the temperature increase, being possible to observe in the thermometer. And analyzing the difference in temperatures with the sulfite sheet and carbon sheet of paper are different, because the light sheet absorbs less heat than the

dark sheet, where consequently increases the temperature....