Lect03 - because • Moving atoms jostle adjacent atoms(in...

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Physics 213 August 31, 2006 3.1 Physics II: Heat & Electromagnetism today: Phase diagrams More on phase changes Heat transfer— conduction, convection, and radiation Physics 213 August 31, 2006 3.2 Phase diagrams The phase of a substance depends on both its temperature T and its pressure p — and can be plotted in a phase diagram : ! ! ! p T Physics 213 August 31, 2006 3.3 A. Cyclohexane has a heat of vaporization of 3.6 ! 10 5 J/kg and a heat of fusion of 3.2 ! 10 4 J/kg. If we start with liquid near the triple point and allow it to evaporate (and freeze) until only vapor and solid are left, about how much of the original mass of liquid will remain as solid? ( Note : no heat is allowed to enter or leave the system.) 1. about 10% 2. about 50% 3. about 90% Physics 213 August 31, 2006 3.4 Heat transfer " Convection Heat flows due to the mass motion of a fluid — no simple equation describes it. # Conduction Heat flows in a stationary substance
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Unformatted text preview: because: • Moving atoms jostle adjacent atoms (in gases, liquids, and non-metallic solids), transferring some of their kinetic energy to them. • Nearly free, moving electrons travel many atomic lengths before jostling other electrons (in metals), transferring some of their kinetic energy to them. Physics 213 August 31, 2006 3.5 Physics 213 August 31, 2006 3.6 B. A 1 cm thick sheet of aluminum ( k = 200 W/m·K) is in contact with a 1 cm thick sheet of steel ( k = 50 W/m·K). The outside surface of the aluminum has a temperature of 10˚C and the outside surface of the steel has a temperature of 20˚C. What is the temperature where the sheets are in contact? 1. 12˚C 2. 15˚C 3. 18˚C 20˚C Al steel 10˚C Physics 213 August 31, 2006 3.7 $ Radiation Heat is transferred by electromagnetic radiation (infrared light, visible light, etc .) Heat current is H = Ae ! T 4...
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Lect03 - because • Moving atoms jostle adjacent atoms(in...

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