Heat conductionHeat conduction is the transfer of energy resulting from temperature differences between adjacent parts of a body. Thermal conductivity is recognized as the exchange of energy between molecules and electrons in the conducting medium. The rate of heat flow in a rod of any material is proportional to the cross section of the rod and the temperature difference between the ends and inversely proportional to the length; that is to say that the rate H is equal to the ratio of the section A of the rod to its length l, multiplied by the temperature difference (T2 - T1) and by the thermal conductivity of the material, denoted by the constant k.Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”?Get the original essayA substance with high thermal conductivity k is a good conductor of heat, while a substance with low thermal conductivity is a poor one conductor of heat or a good thermal insulator. Typical values ​​are 0.093 kilocalories/second-meter-°C for copper (a good thermal conductor) and 0.00003 kilocalories/second-meter-°C for wood (a poor thermal conductor). Convection is the transfer of internal energy into or out of an object by the physical movement of a surrounding fluid which transfers the internal energy with its mass. Although heat is initially transferred between the object and the fluid by conduction, the overall transfer of energy comes from the movement of the fluid. Convection can occur suddenly by the creation of convection cells or can be forced by propelling the fluid through the object or by the object through the fluid. Spontaneous convection can occur by: exposed surface areaviscositydensityconductivityacceleration due to gravityNatural convection occurs because most fluids tend to expand when heated, that is, become less dense and increase due to increased buoyancy. The circulation that occurs in this way explains the uniform heating of water in a kettle or air in a heated room: the heated molecules expand the space as they move at increased speed against each other, rise, then cool and approach again, with an increase in density and resulting subsidence. Forced convection involves the transport of fluid by methods other than those resulting from variation of density with temperature. Examples of convection are the movement of air by a fan or water by a pump. Atmospheric convection currents can be created by local heating effects such as solar radiation or contact with cold surface masses. These convection currents move primarily vertically and are responsible for many atmospheric existences, such as clouds and thunderstorms. Thermal Radiation Thermal radiation is a process by which energy, in the form of electromagnetic radiation, is emitted from a heated surface in all directions and travels directly to its point of origin. absorption at the speed of light. Thermal radiation does not require a dominant medium to transport it. Thermal radiation occurs in wavelengths ranging from the longest infrared rays to the shortest ultraviolet rays through the visible light spectrum. The intensity and distribution of energy in this wavelength range depend on the temperature of the emitting surface. The total radiant thermal energy emitted by a surface is proportional to the fourth power of its total temperature (Stefan-Boltzmann law)..