How to Create and Interpret Energy Diagrams: Difference between revisions
(Created page with "==Thermodynamics== This topics focuses on energy work of a system but it can only deal with a large scale response to heat in a system. '''Thermodynamics''' is the study of...") |
No edit summary |
||
| Line 1: | Line 1: | ||
== | ==Energy Diagrams== | ||
== | ==The Main Idea== | ||
Energy Diagrams are extremely useful for analyzing the interactions between two different objects. These diagrams can also be confusing if not properly understood. This page serves as a resource on how to construct and interpret energy diagrams. Let's get started! | |||
===A Mathematical Model=== | |||
===A Computational Model=== | |||
Vpython is great for modeling this concept. Using vpython, we can model many different systems that have kinetic and potential energy. We can model a spacecraft orbiting the Earth, and we can create graphs to display the kinetic, potential, and kinetic+potential energies of this system. See this code for how to do this! | |||
[Sample Vpython code:https://trinket.io/glowscript/4010e21bc3] | |||
===First Law=== | ===First Law=== | ||
Revision as of 12:49, 29 November 2015
Energy Diagrams
The Main Idea
Energy Diagrams are extremely useful for analyzing the interactions between two different objects. These diagrams can also be confusing if not properly understood. This page serves as a resource on how to construct and interpret energy diagrams. Let's get started!
A Mathematical Model
A Computational Model
Vpython is great for modeling this concept. Using vpython, we can model many different systems that have kinetic and potential energy. We can model a spacecraft orbiting the Earth, and we can create graphs to display the kinetic, potential, and kinetic+potential energies of this system. See this code for how to do this!
[Sample Vpython code:https://trinket.io/glowscript/4010e21bc3]
First Law
The first law of thermodynamics defines the internal energy (E) as equal to the difference between heat transfer (Q) into a system and work (W) done by the system. Heat removed from a system would be given a negative sign and heat applied to the system would be given a positive sign. Internal energy can be converted into other types of energy because it acts like potential energy. Heat and work, however, cannot be stored or conserved independently because they depend on the process. This allows for many different possible states of a system to exist. There can be a process known as the adiabatic process in which there is no heat transfer. This occurs when a system is full insulated from the outside environment. The implementation of this law also brings about another useful state variable, enthalpy.
A Mathematical Model
E2 - E1 = Q - W
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
- How is this topic connected to something that you are interested in?
- How is it connected to your major?
- Is there an interesting industrial application?
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.
See also
Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?
Further reading
Books, Articles or other print media on this topic
External links
Internet resources on this topic
References
https://www.grc.nasa.gov/www/k-12/airplane/thermo0.html http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thereq.html https://www.grc.nasa.gov/www/k-12/airplane/thermo2.html http://www.phys.nthu.edu.tw/~thschang/notes/GP21.pdf http://www.eoearth.org/view/article/153532/