1. Conduction
Conduction is heat transfer from metal (solid) that is not involving the transferred of the metal particles. For example, if you heat metal end, a few moments later the other end will be heated as well. It suggests that there is a heat transfer in metal. The heat is propagating from the high to low temperature ends. In other words, the heat transfer could only take places when there is a difference in temperature. If there isn’t, there would never be any heat transfer.
If it is heated, the kinetic energy of a substance’s particles is likely to increase. Keep in mind, all substance particles are vibrating. Since the kinetic energy increase, the particles influence the vibration of the neighboring around it. As the result, the particle vibration is increasing as well. Then, the neighboring particles influence the next neighboring particle’s vibration. In this case, the substance particles are not migrating. It is the substance particle’s kinetic energy that is migrating . The amount of the particle’s kinetic energy is proportional to its temperature.
Based on the conductivity, substance could be divided into conductor and isolator. Conductor is a substance that can transmit heat easily, while isolator is the one that is hard to transmit heat.
2. Convection
Convection is a heat transfer that emerges due to the presence of the intermediate substance’s particle flow. In this, the heat is flowing with the particle flow. Heat transfer in convection occurs in fluids, in example water and air. The water or air flow take place in two ways, those are naturally flowing and forced to flow. Therefore, heat transfer in convection could be divided into two, namely natural and forced convections.
a. Water Flow Vertically
The heated water will decrease in its mass density so that the weight decreases as well. As the result, the water moves upwards and its position is occupied by the water with greater mass density (cold water). During the heating, it will proceed continuously so that the vertical water flow would occur. That water flow that causes the heat to be spread to all parts of the water.
b. The Occurrence of Land and Sea Winds
At noon, the air temperature in land is higher than in the sea. The air in land with mass density of which is lower will raise and its place will be occupied by the cooler air. Therefore, the air flow occurs from the sea to the land referred as sea wind. Conversely, at night, the air temperature in land is lower than in the sea. This is due to the land can get cooler faster at night. As the result, there air flows from the land to the sea referred as land wind. During the shift of land and sea wind, we feel that there is almost no wind in the beach. When and why does it happen?
The example of convection discussed above is the natural one. The example of forced convection are, among others, the raise of water for being pumped with water pump and the entrance of water into the tire using a pump.
3. Radiation
There is a vacuum between the earth and sun. Heat can transfer through heat gh a vacuum. It is proved with the ability of the sun’s rays to achieve the earth. Heat transfer through a vacuum is done through radiation. In this case, the heat is radiated in the form of electromagnetic wave. Thus, electromagnetic wave propagates through a vacuum.
Every hot object radiates its heat in the form of electromagnetic wave. The radiated electromagnetic wave has certain wave length and frequency, depending on the temperature. If it reaches an object, electromagnetic wave undergoes three treatment possibilities; those are absorbed, reflected, or partly absorbed and partly reflected. However, if it reaches an object, generally, electromagnetic wave will be absorbed partly and the other part will reflected. The electromagnetic will be absorbed entirely if it reaches black objects and will be reflected entirely if it reaches shiny objects.
0 komentar:
Posting Komentar