183_notes:define_energy

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision		 Previous revision
183_notes:define_energy [2015/10/05 14:33] – caballero183_notes:define_energy [2021/03/17 20:43] (current) – [The First Law of Thermodynamics (The Energy Principle)] stumptyl
Line 1: Line 1:
 +
 +Section 6.1 and 6.2 in Matter and Interactions (4th edition) 
 ===== What is Energy? ====== ===== What is Energy? ======
  
Line 5: Line 7:
 //"Energy is a numerical quantity, which does not change when something happens...."// //"Energy is a numerical quantity, which does not change when something happens...."//
  
-The above quotes come from [[http://en.wikipedia.org/wiki/Richard_Feynman|Richard Feynmann]], a 20th century physicist who is thought to have some of the greatest insights into the physical world. He's being a bit flippant about our knowledge of energy, but he's not wrong. We don't know what energy is. We know that energy is a conserved quantity. That is, you can track the energy of a system and see that it changes forms, but it is not created or destroyed. In this set of notes, you will read a brief bit about the history of different energy ideas, about the different forms of energy, and the first law of thermodynamics (conservation of energy).+The above quotes come from [[http://en.wikipedia.org/wiki/Richard_Feynman|Richard Feynmann]], a 20th century physicist who is thought to have some of the greatest insights into the physical world. He's being a bit flippant about our knowledge of energy, but he's not wrong. We don't know what energy is. We know that energy is a conserved quantity. That is, you can track the energy of a system and see that it changes forms, but it is not created or destroyed. **In this set of notes, you will read a brief bit about the history of different energy ideas, about the different forms of energy, and the first law of thermodynamics (conservation of energy).**
  
 ==== Lecture Video ==== ==== Lecture Video ====
Line 22: Line 24:
 While energy is difficult to define absolutely, it takes a number of different forms.  While energy is difficult to define absolutely, it takes a number of different forms. 
  
-//Kinetic// energy is the energy associated with the motion of systems, which can be individual objects or collections of objects. //Thermal// energy can be thought of as a microscopic form of kinetic energy. +**Kinetic energy** is the energy associated with the motion of systems, which can be individual objects or collections of objects. **Thermal energy** can be thought of as a microscopic form of kinetic energy. 
  
-//Potential// energy arises from the interactions between pairs of objects. These are manifest in gravitational interactions (//gravitational// potential energy) and electrostatic interactions (//electrostatic//, //elastic//, and //chemical// potential energy).+**Potential energy** arises from the interactions between pairs of objects. These are manifest in gravitational interactions (gravitational potential energy) and electrostatic interactions (electrostatic, elastic, and chemical potential energy).
  
-There are two other forms of energy that you might be aware of: //radiant// energy associated with light, and the //mass// energy associated with objects that have mass.+There are two other forms of energy that you might be aware of: **radiant energy** associated with light, and the **mass energy** associated with objects that have mass.
  
 While there are many forms of energy, almost all forms of energy used by us can be traced back to the sun. Think about the energy flow that occurs use a hand crank flashlight. While there are many forms of energy, almost all forms of energy used by us can be traced back to the sun. Think about the energy flow that occurs use a hand crank flashlight.
Line 34: Line 36:
 ==== The First Law of Thermodynamics (The Energy Principle) ==== ==== The First Law of Thermodynamics (The Energy Principle) ====
  
-{{ 183_notes:system_and_surroundings.002.png?300}}+{{ 183_notes:week7_sysvssurroundings.png?300}}
  
-The first law of thermodynamics (or the energy principle) governs when energy moves into and out of systems. In other words, //the work that is done is equal to the energy that is transferred or transformed.// For this to make sense, you have to define a system and track how the energy of that system ($E_{sys}$) changes as a result of work done by the surroundings ($W_{surr}$) and the heat exchanged with the surroundings ($Q$). Mathematically, you can write this relationship as the energy principle,+The first law of thermodynamics (or the energy principle) governs when energy moves into and out of systems. In other words, __**the work that is done is equal to the energy that is transferred or transformed.**__ For this to make sense, you have to define a system and track how the energy of that system ($E_{sys}$) changes as a result of work done by the surroundings ($W_{surr}$) and the heat exchanged with the surroundings ($Q$). Mathematically, you can write this relationship as the energy principle,
  
 $$\Delta E_{sys} = W_{surr} + Q$$ $$\Delta E_{sys} = W_{surr} + Q$$
  
-This principle tell you precisely how the energy of system will change as a result of interactions with the surroundings.+This principle tells you precisely how the energy of the system will change as a result of interactions with the surroundings.
  • 183_notes/define_energy.1444055623.txt.gz
  • Last modified: 2015/10/05 14:33
  • by caballero