L2 - Temperature Ideal Gas and Equipartition(2)

L2 - Temperature Ideal Gas and Equipartition(2) - Lecture 2...

Info icon This preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 2 1) Temperature & Thermometers 2) Ideal Gas Law → Temperature ~ Kin. Energy 3) Equipartition Theorem Thermal physics - PH2103 Textbooks paragraphs: 1.1; 1.2; 1.3
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Temperature The definition of temperature is not easy. We will only provide a precise definition in a month.. From now on, we consider an operative definition of temperature, “ temperature is what you measure with a thermometer ”. In this lesson: 1) Empirical observations allowing to understand how a thermometer works 2) Ideal gas law the temperature of gases is related to their kinetic energy. 3) Equipartition theorem
Image of page 2
Thermometry Three empirical observations allow for the functioning of thermometers system in thermal contact reach thermal equilibrium zeroth law of thermodynamics there are physical properties we can measure that change with temperature (e.g. volume, pressure, electrical resistance, …) We now have a look at these facts.
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Thermal equilibrium When two objects interact thermally, energy flows from one system to the other until (thermal) equilibrium is attained . At this point, there is an observable which is the same for both systems. We call this observable temperature. Initial state After “some time” energy
Image of page 4
Diffusive equilibrium Total volume: V = V 1 +V 2 Number of particles: N = N 1 +N 2 Q1: How many particles occupy volumes V 1 and V 2 after at long time ? Q2: What fixes how long we have to wait for this condition to occur? V 1 , N 1 (t= ) V 2 , N 2 (t= ) Since it is difficult to think about a flow of “energy”, let's consider a related example, diffusive equilibrium, that involves the flow of particles. We consider two volumes containing particles, separated by a closed valve . Closed valve no particle exchange no diffusive “contact” At time t = 0, we open the valve, and particles start being exchanged.
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Diffusive equilibrium Total volume: V = V 1 +V 2 Number of particles: N = N 1 +N 2 Q1: How many particles occupy volumes V 1 and V 2 after at long time ? Ans: Two volumes have the same density: Q2: What fixes how long we have to wait for this condition to occur? Ans: size of connecting tube i.e. properties of the diffusive contact V 1 , N 1 (t= ) V 2 , N 2 (t= ) equilibrium Relaxation time N 1 = N V 1 V N 2 = N V 2 V N 1 V 1 = N 2 V 2
Image of page 6
Diffusive vs. thermal equilibrium Closed valve No thermal contact Open valve Flux of particles Flux of energy After some time Thermal contact After some time Equilibrium: same density Timescale Diffusive contact Equilibrium: same temperature Timescale Thermal contact Notes: 1) thermal contact does not imply physical contact 2) the “no thermal contact” condition is only ideal; one can only increase the timescale (chemical potential)
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
What do we feel? Large flux of energy from the body to the metal We are not sensible to the temperature of an object, but to the flux of energy we exchange with than object.
Image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern