The First Law of Thermodynamics

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Physics Fluid Mechanics and Thermal Physics

	Heat: Energy in transit:
	Heat may be defined as energy in transit or the flow of energy from a high temperature object to a lower temperature object. Heating an object is when transfer of thermal energy takes place to the object from another object that is at a higher temperature. Due to the transfer of energy internal energy of the object can be increased. The internal energy is the true microscopic form of energy. Thermal energy is the amount of internal kinetic energy and potential energy of an object. It is also simply called internal energy. Temperature is a measure of the average kinetic energy of the particles in an object. An object feels warm or hot if its temperature is higher than our skin. To say something is hot means its temperature is relatively high. Similarly, cooling of an object occurs when thermal energy is transferred from the object to another object that is at a lower temperature. An object feels cool or cold if its temperature is lower than our skin. To say something is coldmeans its temperature is relatively low. Whether heating or cooling, the end result is that the two objects become at the same temperature after a period of time. This is called thermal equilibrium. Thus, at thermal equilibrium two objects have same temperature. The Transfer of Heat: Heat is a form of energy and is called thermal energy or heat energy. The heat energy or thermal energy is transferred from an object of high temperature to the one of lower temperature by conduction, convection and radiation. This is called the transfer of heat or heat transfer or heat flow, although the thermal energy is being transferred. Conduction is the process, when materials are in physical contact and kinetic energy is transferred through the collision their particles. The heat transfer occurs in the solid objects usually through this process. Convection is the process, in which the heat transfer occurs through the movement of the particles. The heat flow in a fluid can occur through the convection process. Radiation is the process, in which the heat transfer occurs without using the intervening medium. Usually the transfer of heat energy occurs through vacuum or air in the process of radiation. .