Mechanical Energy Essay Example

carefully developed fruit of the finding from experiments in physics that in general a definite statement cannot be made of "the amount of heat in a body" although ordinary language appears to suggest that such a statement could be made. Quantity of heat transferred can be estimated either by direct measurement as heat, in calorimetry, or indirectly, by calculations based on other quantities, relying on the law of conservation of energy, or on the first law of thermodynamics.

Heat is primarily of macroscopic character, but it has a good explanation in the motion of microscopic particles. In ordinary language, as distinct from technical language, heat has a broader meaning. [7] This can lead to confusion if the diversity of usage of words is forgotten. [8][9][10][11] Thermodynamically, energy can be produced or transferred as heat by thermal conduction[12], by thermal radiation,[13] by friction and viscosity,[14] and by chemical dissipation. [15][16][17] Heat transfer by conduction and by radiation from a hotter to a colder body is spontaneous.

The second law of thermodynamicsrequires that the transfer of energy from one body to another with an equal or higher temperature can only occur with the aid of aheat pump by mechanical work, or by some other similar process in which entropy is increased in the universe in a manner that compensates for the decrease of entropy in the cooled body, due to the removal of the heat from it. [18] For example, energy may be removed against a temperature gradient by spontaneous evaporation of a liquid.

The engineering discipline of heat transfer recognizes heat transfer by conduction, by convective circulation, by net mass transfer, and by

radiation. In physics, especially in calorimetry, and in meteorology, the concepts of latent heat and of sensible heat are used. A related and potentially confusing term is thermal energy, loosely defined as the energy of a body that increases with its temperature. Gravitational Energy Gravitational Energy where motion, like water going over a dam, is caused by gravity's pull. where motion, like water going over a dam, is caused by gravity's pull.

Gravitational energy is the energy associated with the gravitational field. This phrase is found frequently in scientific writings about quasars (quasi-stellar objects) and other active galaxies. Chemical Energy is the chemical reaction causing changes; food and fuel both store chemical energy. In chemistry, Chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction or, to transform other chemical substances. Template:Fusion Breaking or making of chemical bonds involves energy, which may be either absorbed or evolved from a chemical system.

Energy that can be released (or absorbed) because of a reaction between a set of chemical substances is equal to the difference between the energy content of the products and the reactants. This change in energy is change in internal energy of a chemical reaction. Where is the internal energy of formation of the reactant molecules that can be calculated from the bond energies of the various chemical bonds of the molecules under consideration and is the internal energy of formation of the product molecules.

The internal energy change of a process is equal to the heat change if it is measured under conditions of constant volume, as in a closed rigid container such

as a bomb calorimeter. However, under conditions of constant pressure, as in reactions in vessels open to the atmosphere, the measured heat change is not always equal to the internal energy change, because pressure-volume work also releases or absorbs energy. (The heat change at constant pressure is called the enthalpy change; in this case the enthalpy of formation).

Another useful term is the heat of combustion, which is the energy released due to a combustion reaction and often applied in the study of fuels. Food is similar to hydrocarbon fuel and carbohydrate fuels, and when it is oxidized, its caloric content is similar (though not assessed in the same way as a hydrocarbon fuel — see food energy). In chemical thermodynamics the term used for the chemical potential energy is chemical potential, and for chemical transformation an equation most often used is the Gibbs-Duhem equation Electrical Energy is when motion, light or heat is produced by an electrical current like the electric coils on your stove.

Electric potential energy, or electrostatic potential energy, is a potential energy (measured in joules) that results from conservativeCoulomb forces and is associated with the configuration of a particular set of point charges within a defined system. Not to be confused with the term electric potential (measured in volts), the term "electric potential energy" is used to describe the potential energy in systems withelectric fields that change with time (time variant), while the term "electrostatic potential energy" is used to describe the potential energy in systems with electric fields that do not change with time (time invariant)