Greetings, First law of thermodynamics states: U=Q-W. I am havingtrouble with un
ID: 1747102 • Letter: G
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Greetings, First law of thermodynamics states: U=Q-W. I am havingtrouble with understanding the concepts of this equation and whatit implies when variables change. Examples are below. 1. During an adiabatic (Q=0) process, U=-W. What doesdelta U=-W mean? That internal energy is decreasing when work ispositive (if you switch the signs)? Why does this happen, if mythinking is correct? 2. During constant volume (Work=0): U=Q. What does thismean? That all heat and internal energy is being transfered amongsteach other? 3. And finally, in a closed cycle (U=0), which meansthat Q=W. Does this mean that heat and work are the same? And whyis delta U=0 in a closed cycle? Does this mean that all the heat isheld in a piston without being able to escape? Thanks and will rate high for a simple explanation of thesevariables! Greetings, First law of thermodynamics states: U=Q-W. I am havingtrouble with understanding the concepts of this equation and whatit implies when variables change. Examples are below. 1. During an adiabatic (Q=0) process, U=-W. What doesdelta U=-W mean? That internal energy is decreasing when work ispositive (if you switch the signs)? Why does this happen, if mythinking is correct? 2. During constant volume (Work=0): U=Q. What does thismean? That all heat and internal energy is being transfered amongsteach other? 3. And finally, in a closed cycle (U=0), which meansthat Q=W. Does this mean that heat and work are the same? And whyis delta U=0 in a closed cycle? Does this mean that all the heat isheld in a piston without being able to escape? Thanks and will rate high for a simple explanation of thesevariables!Explanation / Answer
From the First law of Thermodynamics : Q = U + W It can be defined as : The toal amount of heat given to a system is utilised to increase the internal energy of the system and to doexternal workdone. (1) Duringthe adiabatic process : Heat ( Q) remainsconstant , hence Q = 0 From first law : 0 = U + W or U = - W Hence the work decreases it is nothing but positivework. (2) If Volume isconstat , change in volume ( dV) = 0 W = P . dV = 0 From first law : Q = U Hence the toal heat given to a system is utilised toincrease its internal energy. (3) In a closedcycle : U = 0 From first law : Q = W Hence in this process , Heat given to a system isutilised to do the Work. Hope this helps u! Q = U Hence the toal heat given to a system is utilised toincrease its internal energy. (3) In a closedcycle : U = 0 From first law : Q = W Hence in this process , Heat given to a system isutilised to do the Work. Hope this helps u! Q = W Hence in this process , Heat given to a system isutilised to do the Work. Hope this helps u!Related Questions
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