# Differences

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 phy131studiof15:lectures:chapter19 [2015/07/22 11:46]mdawber [Thermal Stress] phy131studiof15:lectures:chapter19 [2015/11/11 08:54] (current)mdawber [Using the Ideal Gas Law to determine Absolute Zero] Both sides previous revision Previous revision 2015/11/11 08:54 mdawber [Using the Ideal Gas Law to determine Absolute Zero] 2015/11/06 09:08 mdawber [Ideal Gas Law] 2015/11/06 09:01 mdawber [Thermal Stress] 2015/11/06 09:00 mdawber [19.P.014] 2015/11/06 08:50 mdawber [Thermal Expansion] 2015/07/22 11:47 mdawber [Thermal Stress] 2015/07/22 11:46 mdawber [What makes a gas ideal?] 2015/07/22 11:46 mdawber [Thermal Stress] 2015/07/22 11:43 mdawber created Next revision Previous revision 2015/11/11 08:54 mdawber [Using the Ideal Gas Law to determine Absolute Zero] 2015/11/06 09:08 mdawber [Ideal Gas Law] 2015/11/06 09:01 mdawber [Thermal Stress] 2015/11/06 09:00 mdawber [19.P.014] 2015/11/06 08:50 mdawber [Thermal Expansion] 2015/07/22 11:47 mdawber [Thermal Stress] 2015/07/22 11:46 mdawber [What makes a gas ideal?] 2015/07/22 11:46 mdawber [Thermal Stress] 2015/07/22 11:43 mdawber created Line 70: Line 70: Coefficients of thermal expansion can be found [[http://​en.wikipedia.org/​wiki/​Thermal_expansion|here]] or your textbook. ​ Coefficients of thermal expansion can be found [[http://​en.wikipedia.org/​wiki/​Thermal_expansion|here]] or your textbook. ​ + + ===== 19.P.014 ===== + + ===== 19.P.017 ===== + + ===== Some Thermal Expansion demos ===== ===== Some Thermal Expansion demos ===== Line 100: Line 106: These stresses can be reduced by the inclusion of [[wp>​Expansion_joint|expansion joints]] in bridges, roads and pipes. These stresses can be reduced by the inclusion of [[wp>​Expansion_joint|expansion joints]] in bridges, roads and pipes. + + ===== 19.P.025 ===== + + + ===== What makes a gas ideal?===== + + There are a number of conditions which must be satisfied for a gas to be considered ideal + + - There must be a large number of molecules and they should move in random directions with a range of different speeds. + - The spacing between molecules should be much greater than the size of the molecules. + - Molecules are assumed to interact only through collisions. + - The collisions are assumed to be elastic. Line 147: Line 165: This equation is the [[wp>​Ideal_gas_law|ideal gas law]] This equation is the [[wp>​Ideal_gas_law|ideal gas law]] + + ===== 19.P.034 ===== + + ===== 19.P.042 ===== + + ===== 19.P.044 ===== + + ===== Ideal Gas Law for a number of molecules ===== ===== Ideal Gas Law for a number of molecules ===== Line 159: Line 185: ===== Using the Ideal Gas Law to determine Absolute Zero ===== ===== Using the Ideal Gas Law to determine Absolute Zero ===== - If $PV=nRT$ the absolute zero temperature occurs when $P=0$. In practice most gases will liquefy before this point, but we can measure the pressure of fixed volume of gas at a couple of reference points and extrapolate down to zero pressure to get an estimate for [[wp>​Absolute_zero|absolute zero]]. + If $PV=nRT$ the absolute zero temperature occurs when $P=0$. In practice most gases will liquefy before this point, but we can measure the pressure of a fixed volume of gas at a couple of reference points and extrapolate down to zero pressure to get an estimate for [[wp>​Absolute_zero|absolute zero]]. Through laser cooling and molecular trapping techniques it is now possible (but difficult!) for temperatures on the order of a $\mathrm{nK}$ to be achieved. Prof. [[http://​ultracold.physics.sunysb.edu/​index.html|Dominik Schneble]] produces ultra-cold ($\mu K$) Bose-Einstein condensates in the basement of this building! Prof. [[http://​www.stonybrook.edu/​metcalf/​hmetcalf.html|Hal Metcalf]] was one of the key players in the original development of laser cooling. Through laser cooling and molecular trapping techniques it is now possible (but difficult!) for temperatures on the order of a $\mathrm{nK}$ to be achieved. Prof. [[http://​ultracold.physics.sunysb.edu/​index.html|Dominik Schneble]] produces ultra-cold ($\mu K$) Bose-Einstein condensates in the basement of this building! Prof. [[http://​www.stonybrook.edu/​metcalf/​hmetcalf.html|Hal Metcalf]] was one of the key players in the original development of laser cooling. - ===== What makes a gas ideal?===== - There are a number of conditions which must be satisfied for a gas to be considered ideal - - - There must be a large number of molecules and they should move in random directions with a range of different speeds. - - The spacing between molecules should be much greater than the size of the molecules. - - Molecules are assumed to interact only through collisions. - - The collisions are assumed to be elastic. 