Topic Energy in thermal processes PHYSICS 231 Current Assignments Homework Set 9 open due Thursday April 7 11pm Reading 11 1 3 11 5 12 5 6 12 8 by next week Tuesday first lecture 4 4 11 Physics 231 Spring 2011 2 Key Concepts Heat Energy change by Heat and Work Heat capacity Thermal equilbrium final temperature when objects with different temperatures come in contact Phase transition Heat of vaporization and heat to fusion Mechanisms of heat transfer conduction convection radiation 4 4 11 Physics 231 Spring 2011 3 Specific heat capacities Air 720 J kg K at about 20 deg C 4 4 11 Physics 231 Spring 2011 4 Molar specific heat This is per mol 4 4 11 Physics 231 Spring 2011 5 Heats of transformation 4 4 11 Physics 231 Spring 2011 6 Video http www youtube com watch v 1PcnCWZP7l0 4 4 11 Physics 231 Spring 2011 7 Conductivities 4 4 11 Physics 231 Spring 2011 8 emissivity Ideal absorber black body e 1 all energy is absorbed also ideal radiator Ideal reflector e 0 no energy is absorbed PHY 231 9 PHY 231 10 Black body A black body is an object that absorbs all electromagnetic radiation that falls onto it They emit radiation depending on their temperature If T 700 K almost no visible light is produced hence a black body The energy emitted from a black body P T4 with 5 67x10 8 W m2K4 b 2 8977685 51 10 3 mK Wiens displacement constant More in PHY232 PHY 231 11 Video http www youtube com watch v 1h1wjKqAcqw http www youtube com watch v fxu1qfwrHu8 4 4 11 Physics 231 Spring 2011 12
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