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Thermal Energy

This topics focuses on the energy and work of a system. Energy transfer is one of the fundamental principals of Physics, thermal energy falls under this category. This type of energy falls under the abbreviation of Q which stands for the heat that is expelled from an object once a reaction or kinetic energy is transferred; as well as the movement of tiny particles within the object. There are three forms of Thermal Energy: Conduction, Convection and Radiation. Conduction is the transfer of heat energy though collisions between adjacent molecules. Convection is the transfer of heat through motion of a fluid such as air or water; when the fluid is heated it is caused to move away from the source of heat, therefore carrying the heat energy with it. Radiation is the transfer of heat through waves or particles through a material or space.

Definitions

E(total) = delta K + delta U + Rest Energy [1]

Units

All types of energy are expressed in Joules. Thermal Energy(Heat) is no different from the other forms of energy with the expression of units; therefore Thermal Energy(Heat) is also expressed in Joules as well.

A Computational Model

You are able to view the transfer of heat through the link provided.[2] This link gives credit to the author, Andi Lucas; it is a video I found interesting and entertaining, however I did not create the video.

First Law

Heat Energy transfer falls under the Law of Thermodynamics. This is defined as the internal energy (E) which is equal to the change of heat transfer (Q) into a system and work (W) done by the system. When heat is removed from a system it results with a negative answer, and when heat is added to a system allows for a positive transfer of heat and thus a positive answer. Heat can not be stored like Potential energy, due to the process that is needed; thus resulting in Kinetic energy. Due to this many different arrangements of the system are able to exist.

Second Law

The second law states that there is another useful variable of heat, entropy (S). Entropy can be described as the disorder or chaos of a system, but in physics, we will just refer to it as another variable like enthalpy or temperature. For any given physical process, the combined entropy of a system and the environment remains a constant if the process can be reversed. The second law also states that if the physical process is irreversible, the combined entropy of the system and the environment must increase. Therefore, the final entropy must be greater than the initial entropy.

Mathematical Models

delta S = delta Q/T Sf = Si (reversible process) Sf > Si (irreversible process)

Examples

Reversible process: Ideally forcing a flow through a constricted pipe, where there are no boundary layers. As the flow moves through the constriction, the pressure, volume and temperature change, but they return to their normal values once they hit the downstream. This return to the variables' original values allows there to be no change in entropy. It is often known as an isentropic process.

Irreversible process: When a hot object and cold object are put in contact with each other, eventually the heat from the hot object will transfer to the cold object and the two will reach the same temperature and stay constant at that temperature, reaching equilibrium. However, once those objects are separated, they will remain at that equilibrium temperature until something else acts upon it. The objects do not go back to their original temperatures so there is a change in entropy.

Connectedness

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History

Thermodynamics was brought up as a science in the 18th and 19th centuries. However, it was first brought up by Galilei, who introduced the concept of temperature and invented the first thermometer. G. Black first introduced the word 'thermodynamics'. Later, G. Wilke introduced another unit of measurement known as the calorie that measures heat. The idea of thermodynamics was brought up by Nicolas Leonard Sadi Carnot. He is often known as "the father of thermodynamics". It all began with the development of the steam engine during the Industrial Revolution. He devised an ideal cycle of operation. During his observations and experimentations, he had the incorrect notion that heat is conserved, however he was able to lay down theorems that led to the development of thermodynamics. In the 20th century, the science of thermodynamics became a conventional term and a basic division of physics. Thermodynamics dealt with the study of general properties of physical systems under equilibrium and the conditions necessary to obtain equilibrium.

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Contents

Thermal Energy

Definitions

Units

A Computational Model

First Law

Second Law

Mathematical Models

Examples

Connectedness

History

See also

Further reading

External links

References

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