Two objects of different temperature had thermal contact each other, the temperature of hotter the object is reduced while a cooler temperature increases. There’s something moving in this case, what is it? Caloric, a material that is not visible, which flows from high temperature objects to low-temperature objects.
Benjamin Thompson / Count Rumford (1753-1814) with his experiments, he drilled metal, it is observed that the drill bits become heated and cooled with water (until the water is boiling), certainly from the theory of “caloric”, caloric these over time will run out and it turns out if the process continues caloric is not depleted, so it is not appropriate caloric theory. So heat is not material.
Heat and Thermal Energy
There is a difference between the heat and energy of a material. Heat is only used when explaining the energy transfer from one place to another. Heat is energy transferred due to different temperature. While the energy in the (thermal) energy is due to the temperature.
When two or more thermal contact occurs there will be a flow of heat from higher temperature object to a lower temperature object, to achieve thermal equilibrium.
This heat transfer process takes place within three mechanisms, namely: conduction, convection and radiation.
1. Conduction heat transfer
The process of heat transfer by conduction when viewed in the atomic kinetic energy exchange between molecules(atoms), in which low energy particles can be increased by mashing the particles with higher energy..Ina place that is heated, the electron energy increase in size and can be given by the collision of electrons surrounding the heat more quickly.
When two or more thermal contact occurs there will be a flow of heat from higher temperature object to a lower temperature object, to achieve thermal equilibrium. This heat transfer process takes place with inthreemechanisms, namely: conduction, convection and radiation.(Munandar, Ariset al. 2003;Page16)
Example a piece of metal is heated at one end then the other end will continue to the heat.
Conductors and insulators
Based on its heat conductivity, substances can be divided into two kinds, they are conductors and insulators. Conductors are substances that either transfer power, such as various types of metals such as aluminum, copper, iron, silicon steel and others. Insulator is a substance that its heat poor conductivity, such as wood, plastic, paper, glass, air and others. Based on the conductor or insulator properties owned by different, we can utilize it best.
• The tools kitchen (pots, pans) irons and radiators are made and the type of metal, such as:
copper, or iron aluminum, because these materials easily conduct heat and fire to food or water is cooked.
• The handle grip on kitchen utensils, handle of iron made iron and wood plastic or ebonite, because these materials are difficult to conduct heat so that it remains safe to touch.
2. The Convection Heat Transfer
Convection is heat transfer through a substance is accompanied by movement of the particles of that material. Heat transfer by convection occurs in liquids and gases. The occurrence of convection currents in fluids and gas attributed to differences in the density of the substance. In part that is heated, the density of the substance is smaller than the parts that are not heated.
At home ventilation system air natural convection occurs, in which the hot air inside the house moving upward and out through the vents, then the place replaced by the incoming cold air that enter the vents so that the temperature inside the house feel more comfortable. The occurrence of onshore winds and sea breezes are also caused by natural air convection.
By the time we heat water on the stove using a saucepan, heat propagation will occur from the water in the bottom of the pan to the surface by convection. Based on observation, as this heat transfer occurs in a substance that flows, as in liquids and gases.Convection heat transfer in different heat transfer in conduction, convection, where the incident occurred a mass movement or the movement of particles of intermediate particles, whereas the conduction events, this does not happen.
The move took place because they kind of mass differences. Due to the heat, the density of the substance at the bottom (which is closer to the heat source) will be reduced, so that will be lighter than the substance in it. This light causes the substance to move upward, while the heavier substances will move downward. So forth, so that the water in the pan will continue to go up and down spins.
If the heat motion of particles moving in a way that has been heated to say the heat transfer by convection. If the displacement is due to density differences is called natural convection (natural convection) and, if encouraged, for example with a fan or pump is called forced convection (forced convection).
The amount of convection depends on:
a. Body surface area in contact with fluid (A).
b. The temperature difference between surface objects with fluid (T).
c. Convection coefficient (h), which depends on:
• Fluid viscosity
• Fluid velocity
• Difference temperature between surface and fluid
• Heat capacity of fluid
• Mass density of fluid
• Shape of the contact surface
3. The Heat Transfer of Radiation
Radiation is heat transfer in the form of electromagnetic waves. In radiation, heat or energy propagates without the need for an intermediary substance, unlike the case with conduction or convection is always in need of a medium.
Examples of heat transfer by radiation, among others:
a. Heat transfer and the sun on earth.
b. Heat transfer and a fire to objects around it.
Higher and higher the temperature of an object than the temperature of their environment, the greater the beam of heat. In addition to temperature, the amount of heat emitted by an object is also determined by the surface of the object:
a. Black and dull surface is a good absorber of heat radiation as well as transmitter of radiation good heat as well.
b. White and glossy surface is a poor absorber of heat radiation as well as a poor transmitter of heat as well.
c. To reduce the heat climbed to radiation, the surface should be coated with a material to be polished (eg, silver)
When an object receives radiant heat, then the object will experience:
a. Continuing heat (diaterman), eg air.
b. Reflect heat, for example: the mirror.
c. Absorbs heat (aterman), eg glass, water.
To investigate the radiation of heat is used a tool called thermo scope. Thermo scope that can be used to investigate the properties of jets and a variety of surfaces called differential thermos scope.
With differential thermos scope among others, can be determined that the object which emits a dull black surface absorbs heat and was better than a white object surface.
Virtually every object emits and absorbs radiation energy. There are glowing hot objects, and some are not glowing. The second object is dispersive / radiate heat energy in the form of electromagnetic waves with different wavelengths.
Joseph Stefan finds that the rate of propagation of heat by radiation per unit area of surface will depend on the nature and temperature of the object surface. Shiny objects disperse heat more difficult than things that black and dull. This situation also applies to objects that absorb heat. The surface shiny objects more difficult to absorb heat than things that the surface are black and dull. So it can be said that black and dull object is a radio transmitter and a good heat absorber.
In physics, dark matter (English black body) is an object that absorbs all electromagnetic radiation that falls to him, no radiation can escape or reflected.
Even so, in theory of black body also emits all wavelengths of energy are possible. The number and type of electromagnetic radiation it emits black body temperature depends on the
is the ability of an object to emit energy (in the form of electromagnetic waves). The greater the emissivity of the object, the easier it is emitting energy. The value of e between 0 s / d 1. At a value of 0 is usually light colored objects are worth a dark color.
Matter is anything that occupies space and has mass. In principle, all materials can be in three states namely, solid, liquid, and gas. Gaseous substance that has the particles apart and its appeal is very small or almost nonexistent. Substances that are solid attraction between particles is very strong and very close distance while the liquid is between gas and solid, both the distance and the particle as well as its appeal.