What is Themodynamics: Definition and 21 Discussions

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  1. A

    B Efficient way to warm a concave body such as Pita bread

    What is the optimal and efficient way to warm a concave body on a plain source of heat (such as heating concave pita bread) on its peak top or opposite (on the larger surface with gap)? Imagine you have a body in U shape. Is the best way to warm it with the U position or opposite?
  2. A

    Irreversible isothermal Process Work External pressure not provided

    It is clear that the process is isothermal else it is not possible to find heat absorbed. $$W=-P_{ext}(\Delta V)$$ However ##P_{ext}## is not given. How do I proceed? I tried taking ##W=-(P_2V_2-P_1V_1+P_3V_3-P_2V_2)=\Delta(PV)## but it is wrong for obvious reasons.
  3. N

    Thermodynamics - Hot copper block dropped in ice water

    1) Q=m*L -.10*333 2)Q=mc deltat -.10*381*180-0 im unsure about the rest
  4. tracker890 Source h

    Change in system entropy in relation to heat transfer

    Q: What are the differences between the heat transfer calculated by the energy conservation equation and the heat transfer determined by the Gibbs relation? ##why\ \left( ans\_1 \right) \ne \left( ans\_2 \right) ## reference Energy balance: $$ Q_{in,net}-W_{out,net}=\cancel{\bigtriangleup...
  5. Govind

    Gibbs free energy of activation and activation energy

    Let's consider a reaction A (reactant) -> B(product) and activated complex is denoted by C. This graph ( potential energy vs reaction coordinate ) tells us that reactant need some amount of activation energy (Ea) to convert in product, which has low potential energy which is shown here in...
  6. tracker890 Source h

    Q: Rankine cycle pump work Integration

    Why is the process from state 1 to state 2 an isentropic and isovolumic process, but the input work of the pump is (A) not (B)? isovolumic process: $$ w_{pump,in}=\ \int_{1}^{2}{vdp\ =\ v\left(p_2-p_1\right)}\ldots\ldots\ldots\ldots..\left(A\right) $$ isentropic process: $$ \because pv^k=c\ \...
  7. EddieP

    Thermal expansion of air bubbles in plastic

    I am interested in the potential for air bubbles in a plastic structure to expand with heat, and put pressure on the plastic surrounding the air bubble. In this case the plastic structure is formed by melting a thermoplastic powder. In between the grains of powder are voids with air in them. As...
  8. Harikesh_33

    B Question regarding using the expression $dE_{int}$=nC_vdT$

    The first law of Thermodynamics states that the change in Internal energy is equal to the sum of Heat gained or lost by the system and work done by the system or on the system . $dE=Q-W$...(1). In an Adiabatic process ,Q=0 . Therefore $dE=-W$ . Now...
  9. Simobartz

    I Minimization of thermodynamic equilibrium

    Hi, I don't understand what does it mean that at equilibrium the proper thermodynamic potential of the system is minimized. For example on the book Herbert B. Callen - Thermodynamics and an Introduction to Thermostatistics it is written: Helmholtz Potential Minimum Principle. The equilibrium...
  10. Simobartz

    I Request for an example of minimum energy principle (thermodynamics)

    Summary: Request for an example of minimum energy principle usage The minimum energy principle states that, for a system at constant entropy, volume and other extensive quantities, the internal energy is minimized at equilibrium. Can you give me an example in which, using this principle, is it...
  11. R

    Enthelpy and Isentropic compression/expansion

    In a certain thermodynamics textbook, specific work done by an isentropic compressor/pump in an ideal rankine cycles, is given by the following; Wpump = h2 - h1 Wpump = v(P2 - P1), where v = v1 When I carry out these two calculations between any two states, I get vastly different answers...
  12. Mayan Fung

    Relating the entropy of an ideal gas with partial derivatives

    It looks very easy at first glance. However, the variable S is a variable in the given expression. I have no clue to relate the partial derivatives to entropy and the number of particles.
  13. K

    Heat Question -- Temperature rise of a hiker on a long hike

    Homework Statement A 80.4 kg hiker uses 212 kcal hr-1 (3 s.f.) of energy whilst hiking. Assuming that 20% of this energy goes into useful work and the other 80% is converted to heat within the body, calculate the temperature change, in units of Kelvin (K), of the hiker's body during a 1.6 hour...
  14. B

    What is the molar heat capacity of an ideal gas at constant pressure and volume?

    Homework Statement 117 J of energy is supplied as heat to 2.00 moles of an ideal gas at constant pressure, the temperature rises by 2.00 K. Calculate the molar heat capacity at constant pressure C_p,m and the molar heat capacity at constant volume C_v,m for the gas. Is the gas monatomic or...
  15. olgkd123

    How does compression cool water in a household water cooler?

    How does compression cool water in a household water cooler? I was reading and it says, " The water inside the water cooler is fed into a reservoir, where it is cooled using a refrigerant. A refrigerant is a cooling medium that is circulated in pipes that are located close to the reservoir in...
  16. E

    Themodynamics: calculating the partial pressure with Dalton's Law

    Homework Statement In a sealed container is Helium ##M_{He} = \frac {4kg} {kmol} ## with a pressure of ## p_{He} = 4bar##. now is Methan put isothermic inside the container till both the methan and the helium mass are equal( ##M_{CH4} = \frac {16kg} {kmol} ## Calculate using the ideal gas law...
  17. Hamal_Arietis

    Classical Are There Good Thermodynamics and Optics Books for Physics Students?

    Hi I'm a physics student in university, I want to find a book about general thermodynamics which has great and interesting problems. Includes a bit of statistical physics and molecular physics. And a book has theory and problems about optics, wave optics and geometrical optics. Thanks for helping
  18. B

    Ice sublimating to water vapor

    Suppose an ice cube is in a vessel and it is at a temperature slightly below 0 degrees Cesius. Suppose further that the inside of the vessel is a vacuum. If the temperature of the vessel is increased to slightly above zero Celsius and the vacuum is maintained would the state change in the ice...
  19. It's me

    Callen Thermodynamics 2.8-2 matter flow equilibrium

    Homework Statement A two component gaseous system has a fundamental equation of the form $$S=AU^{1/3} V^{1/3} N^{1/3} + \frac{BN_1N_2}{N}$$ where $$N=N_1+N_2$$ and A and B are positive constants. A closed cylinder of total volume 2V_0 is separated into two equal subvolumes by a rigid diathermal...
  20. S

    Solve Thermodynamics Problem: Expansion Irreversibly and Isothermally at 27°C

    Expansion irreversibly and isothermally of an ideal has from a volume of 2dm3 to 10 dm3 against a const pressure of 1 atm at 27 C .Find entropy change of the system and also surroundings due to the process. Heres my attempt: delta S=energy absorbed/temp for the system, = energy...
  21. P

    Reactions and Themodynamics Related Question

    1.) (a) Give the reaction, with molecular structures, of 2-propanol with KMnO4 and 1-pentanol with KMnO4 and calculate the differences in the average bond energies of the reactants and products (ignore KMnO4 and any other side reactions in the calculations). Answer:- the reaction, with...