Lecture08-05.1-Chemical_Potential

Lecture08-05.1-Chemical_Potential - 1 Homework scores...

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Unformatted text preview: 1 Homework scores Scores & Statistics are available on blackboard Last chapter: Debye model of solids: phonons Low temperature limit: D τ τ << D τ τ >> High temperature limit: (Debye law) Planck Blackbody Radiation Stefan-Boltzmann Law Johnson’s noise in resistors: (Planck law in one dimension) 2 4 V R f τ = Δ (Or shot noise, thermal noise) 2 Example: green house effect 1. What would be the temperature of black body exposed to sunlight on the Earth’s orbit? Radiative sunlight flux at Earth’s distance: J sun = 1360 W/m 2 Total energy absorbed: 2 in sun U J R π = Total energy emitted: ( ) 2 4 out out U J T R π = 4 U B J T σ = 2 4 3 2 8 2 4 60 5.670 10 B B k c Wm K σ π--- ≡ = × p 4 2 4 B T R σ π = 2 4 2 4 sun B J R T R π σ π = Equilibrium: 4 4 278 5 41 sun B T J K C F σ = = = = Note: >100,000 TW falls onto Earth. Humankind will need ~50 TW by year 2050 ~200x200 miles area Example: green house effect 1. What would be the temperature of black body exposed to sunlight on the Earth’s orbit? 4 4 278 5 41 sun B T J K C F σ = = = = Earth’s average temperature: 14ºC or 57 F How can we get higher temperature? 3 Example: green house effect Assume: all of the heat radiation from black body is absorbed by atmosphere and re-emitted in all directions What changes? visible Example: green house effect 1. What would be the temperature of black body exposed to sunlight on the Earth’s orbit if there is maximum green house effect ? Radiative sunlight flux: J sun = 1360 W/m 2 Total energy absorbed: 2 in sun U J R π = Total energy emitted: ( ) 2 4 out out U J T R π = 4 U B J T σ = 2 4 3 2 8 2 4 60 5.670 10 B B k c Wm K σ π--- ≡ = × p 4 2 4 B T R σ π = 2 4 2 4 sun B J R T R π σ π = Equilibrium: 4 4 278 5 41 sun B T J K C F σ = = = = ½ 2 4 2 331K = 58C = 136F 4 Green house effect: reality Global CO 2 Emissions 5 Global CO 2 Emissions http://www.grida.no/publications/vg/climate/page/3057.aspx Today Chapter 5 (part 1) Chemical Potential A new conjugate pair: Chemical potential and particle number Definition of chemical potential Ideal gas chemical potential Total, Internal, and External chemical potential Examples: Pressure vs. Altitude Spins in magnetic field Lead-Acid battery 6 Systems Exchanging Particles heat exchange particle...
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This note was uploaded on 12/14/2010 for the course PHYSICS 416 taught by Professor Savikhin during the Spring '10 term at Purdue.

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Lecture08-05.1-Chemical_Potential - 1 Homework scores...

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