Physics Help Forum efficiency proof

 Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Jan 1st 2019, 06:51 AM #1 Junior Member   Join Date: Dec 2018 Location: The 'Milky Way' Galaxy Posts: 13 efficiency proof How is this proved? Efficiency of a battery is: |delta G| *100 ---------------- |delta H| where delta G-change in gibbs free energy delta H-change in enthalpy.
 Jan 1st 2019, 10:53 AM #2 Senior Member   Join Date: Aug 2010 Posts: 383 There is no "proof" it is a definition! topsquark likes this.
 Jan 1st 2019, 11:09 AM #3 Junior Member   Join Date: Dec 2018 Location: The 'Milky Way' Galaxy Posts: 13 Somehow it is concluded. I just want to know how.
 Jan 2nd 2019, 05:02 AM #4 Senior Member   Join Date: Aug 2010 Posts: 383 Then what do you mean by "efficiency of a battery"? What definition are you using? topsquark likes this.
 Jan 2nd 2019, 12:45 PM #5 Forum Admin     Join Date: Apr 2008 Location: On the dance floor, baby! Posts: 2,493 Typically an efficiency is defined based either on the work done by the system divided by work done on the system. This usually involves the entropy change of the system or, in more practical to measure terms, the temperature change in the system. But, as HallsofIvy mentioned, different definitions are simpler to employ for different systems. Take a look at the entropy. That's all I can think of to start with. -Dan __________________ Do not meddle in the affairs of dragons for you are crunchy and taste good with ketchup. See the forum rules here.
 Jan 4th 2019, 11:30 AM #6 Senior Member     Join Date: Jun 2016 Location: England Posts: 691 If I ever knew the terms you use in your efficiency equation, I have long since forgotten. (I might be able to hear a vague tinkle of the recognition bell, but I'm not sure) However, efficiency is essentially How much can actually be got out of the system (the battery in this case) divided by how much could ideally be got out of the system. Ideally (100% efficiency) you would get everything out that you put in. For a battery you put in the chemical energy, you get out electrical energy. How do the terms in your equation relate to these quantities? Note that I suspect the "100" in the equation is to present the efficiency as a percentage (rather than as a number between 0 and 1). topsquark and mak29 like this. __________________ ~\o/~

 Tags efficiency, proof

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post avito009 Philosophy of Physics 2 Jan 20th 2018 05:49 PM Torgny Advanced Electricity and Magnetism 2 Jul 20th 2017 06:45 AM Torgny Advanced Thermodynamics 0 Sep 6th 2016 02:40 PM helloworld101 Kinematics and Dynamics 8 Nov 20th 2009 10:17 AM mattc Kinematics and Dynamics 1 Oct 21st 2009 01:14 AM