Thermodynamics Definition and 1000 Threads

Do you need to know thermodynamics to be a great plumber?How much thermodynamics do you need to know?All of it including the first and second principles of thermodynamics?I want to become one and I don't know how much physics is required to become one.Can you help me? Also are pV,pT and VT...

1. In vacuum and weightlessness, at the bottom of a cylindrical vessel (a cup), there is a layer of solid substance of molar mass µ. This substance sublimes slowly (evaporates from the solid phase into gaseous phase) and pushes thereby the vessel to the opposite direction. Estimate the terminal...

1. Consider a balloon which has thick rigid walls and from which all the air has been pumped out. Now, the valve of the balloon is slightly opened, and the balloon is slowly filled with the air from outside. Find the temperature of the air inside the balloon once the air flow has stopped (since...

Hi! Basically I have some tasks in thermodynamics calculating the heat transfer through a wall. I have been attempting to solve the following problem: “Calculate the heat transfer through the exterior wall in a building, where the temperature inside the building is 20 °C and the temperature...

I am trying to figure out how you can subcool a dewar of liquid oxygen (vacuum insulated) just by releasing the pressure sitting on top of it. The liquid I am thinking of in this case is liquid oxygen, which boils at -297.33 F at 1 atm. Let's say I fill a dewar with LO2, then pressurize that...

I've got a question that requires me to use the Van der Waals equation in the form: p(V-b)=nRT The process is isobaric, the volume changes from 1m3 to 2m3, and there is 1 mole of the unidentified gas. Ultimately, I need to find initial and final values of T. So I rearranged the formula...

Can you understand thermodynamics without a lot of information from chemistry?I mean I didn't learned a lot about atoms,molecules and everything that is related to science so I was wondering if it is possible to learn it without these subjects.I learned a few things about chemistry in high...

Starting from the definition of energy levels ##e_n## and occupations ##a_n## and the conditions ##\sum_n a_n = N## (2.2) and ##\sum_n a_n e_n = E## (2.3) where ##N## and ##E## are fixed I'm trying to find the distribution which extremizes the Shannon entropy. Using the frequency ##f_n=a_n/N##...

I would argue that if you are computing the work done by an expanding gas in a frictionless piston, in an irreversible expansion where the inner pressure is greater at all times than the (constant) outer pressure, that you should integrate the internal pressure over volume change, not multiply...

It seems to me that if one had a functional Alcubierre drive and used it there would be some subluminal frame of reference in which time was going backwards for the spaceship which probably for it and for macroscopic objects in it which constitute a reasonably closed system would be a violation...

Looking through the book of abstracts for «XXI International Conference on Chemical Thermodynamics in Russia (RCCT-2017)» I came across the abstract of talk given by Peter Atkins (University of Oxford) titled «Thoughts about thermodynamics» (you'll find the whole abstract at the end of the...

Homework Statement Using the data presented in the accompanying pressure-versus-volume graph, estimate the work done (including the algerbraic sign) when the system changes from A to B to C along the path shown. Homework Equations The work done is the area from change in position and time...

I still confuse about COP of refrigerator. When i read some journal, it is said that COP of VCRS can be greater than 1 (usually 2 - 4). But, why the COP other than VCRS usally lower than 1? like vortex tube, vapour absorption refrigeration system, etc. Actually, now i am doing a research about...

Homework Statement Find the mass of water that vaporizes when 3.02 kg of mercury at 223 °C is added to 0.347 kg of water at 83.4 °C. Homework Equations Mercury Q = Water Q + Water mL mc∆t= mc∆t + mL The Attempt at a Solution mass of vapor = ((3.02)(140)(223-tfinal) - (4186)(.347)(change in...

The partition function should essentially be the sum of probabilities of being in various states, I believe. Why is it then the sum of Boltzmann factors even for fermions and bosons? I've never seen a good motivation for this in literature.

Greg Bernhardt submitted a new PF Insights post How to Better Define Information in Physics Continue reading the Original PF Insights Post.

hello everyone, recently i was studying thermodynamics and i think i got a basic doubt on what my book has to say and although i feel this is a small thing to ask but since i have no teacher with me, this is the best place i can think of. so my book was saying about intensive and extensive...

Do the laws of thermodynamics basically establish its properties? I got to thinking, and it seems that the main purpose of the laws of thermodynamics is to establish that the thermodynamic properties. 0th & 3rd - establish Termperature as a valid property via ability to have equality & scale...

Homework Statement 12kg of a fluid per minute goes through a reversible steady flow process. The properties of fluid at the inlet are p1 = 1.4bar, ρ1 = 25kg/m3, C1= 120m/s and u1= 920kJ/kg and at the exit are p2= 5.6bar, ρ 2= 5 kg/m3, C2= 180m/s and u2 Homework Equations u1 + P1V1 + (C1)2/2 +...

Ok, so just a quick question, first law of thermodynamics basically states that matter cannot be created nor destroyed aka it can only change states and turn into energy or vice versa, the second law states that, IIRC, for perfect isolated systems entropy remains constant but for our universe...

Greetings! I've been brushing up on some thermodynamics recently and came across a perplexing sentence in my notes and text from undergrad. It says that for a combustion reaction, such as the combustion of heptane: C7H16 (l) + 11O2 (g) ---> 7CO2 (g) + 8H2O (l) That this process carried out at...

I have my first question. It's about entropy in the Carnot cycle and I'll try to be direct. The equal sign in the Carnot cycle efficiency equation is related to the fact that the total entropy doesn't change at the end of the whole cycle (being related to the fact that the heat exchanges occur...

Homework Statement We put 1kg iron of temperature 100 Celsius into container with 1kg of ice, temperature 0 Celsius. What is state of the system after reaching equilibrium? Calculate change of entropy. Coefficient of melting of ice (c_L) is 330 kJ/kg, coefficient of heat transfer of iron (c_I)...

Hello, I'm a engineering student currently taking Thermodynamics and we have this project for our finals which is a sort of reeling /towing device, the assignment consists in a reeling motor that has to tow a small car up along a slope, loaded with a certain weight, the team that is able to...

Hi, Joule's original gas expansion experiment is often presented like in the following link: http://demonstrations.wolfram.com/JouleExperimentOnFreeExpansion/ The apparent lack of temperature change in this experiment is often used in textbooks to demonstrate that the energy of an ideal gas is...

From wikipedia, The general equation is $$\frac{df}{dt} = (\frac{∂f}{∂t})_{force}+(\frac{∂f}{∂t})_{diff}+(\frac{∂f}{∂t})_{coll}$$ where the "force" term external force, the "diff" term represents the diffusion of particles, and "coll" is the collision term. So shouldn't be df/dt=0 when it is...

Hello all, I have been having some problems and would appreciate any help: I have a length of insulated pipe filled with engine oil at rest, the variables are as follows: Toil: 40 oC Tair: 5 oC h1 (LO): 3600.63 W/m2/K r1 (pipe inner): 0.1 m r2 (pipe outer): 0.1095 m r3...

I know that dS=dQ/T for reversible process, is dU=TdS-PdV for reversible process only?

I have to calculate the efficiency of the above cycle for an ideal gas, that goes at the order a-b-c-a: I know that the answer is 16/97 but I can't calculate the heat in the a-b stage.

Homework Statement Calculate the change in molar entropy of steam heated from 100 to 120 °C at constant volume in units J/K/mol (assume ideal gas behaviour). Homework Equations dS = n Cv ln(T1/T0) T: absolute temperature The Attempt at a Solution 100 C = 373.15 K 120 C = 393.15 K dS = nCvln...

Homework Statement A careless farmer sends this sheep out to graze on a very cold winter day when the temperature is -10oC. The sheep's coat has a thickness of 4.7 cm and a surface area 1.3 m2. Calculate the rate of heat loss from the sheep on this cold day. Assume that heat is lost only...

In deriving the Carnot Efficiency, the assumption is made that theoretically most efficient engine will generate no net entropy, meaning that the entropy that enters the system during heat absorption must equal the entropy that leaves the engine during heat rejection. Why is the case? Why would...

Homework Statement From a previous post in this forum, unfortunately the thread is closed for answers otherwise I would have posted it there: https://www.physicsforums.com/threads/thermodynamic-filling-of-tank-matlab.479112/ A 70 ft3 rigid insulated tank contains air at 14.7 psia and 80 º F...

Homework Statement Compare the compressor work input required to compress water isentropically from 100kpa to 1MPa, assuming that the water exists as (a) saturated liquid and (b) saturated vapor at the inlet state Homework Equations Win = v(P2-P1) Win = (h2- h1) The Attempt at a Solution...

Homework Statement Adiabatic expansion of an ideal gas is carried out in a steady flow process. The initial pressure of the gas is 2.5 bar. The volume is expanded from 1.2m3 to 3.8m3. Heat capacity ratio (γ) = 1.42. Calculate enthalpy change of the process. Homework Equations PV = nRT W = ∫...

Homework Statement The problem is "A multicylinder gasoline engine in an airplane, operating at 2.40 10^3 rev/min, takes in energy 7.98 10^3 J and exhausts 4.50 10^3 J for each revolution of the crankshaft." and it wants me to find the liters of fuel consumed in 1 hr of operation if the heat...

Homework Statement A freshly-forged iron horseshoe, with a mass of 0.549 kg is dropped into a 0.281 kg iron pot which contains 1.60 kg of water at 21.4 oC. After the horseshoe, pot and water reach thermal equilibrium they have a temperature of 29.8 oC. Assuming the pot and the water were in...

Homework Statement A 77.1 kg hiker uses 191 kcal hr-1 (converted to 222.133 J.s ?) 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...

Homework Statement A 4.96 kg piece of solid material is heated from 16.7oC to 234oC (3 s.f.) using 725 kJ of energy (3 s.f.). Assuming an efficiency of 0.342 for the heating process, and that the material does not melt, calculate the specific heat capacity of the material. m = 4.96 kg change...

Homework Statement A concrete driveway is built from identical slabs of concrete, as shown below, which have a length, L, of 3.18 m long at 17.3 C. The concrete slabs have coefficient of linear expansion of 1.20 x 10-5 K-1 and are laid in an area where the temperature ranges from -29.8 C to...

Homework Statement Homework EquationsThe Attempt at a Solution I understand how they got Q1 and Q2 for the first two columns, but how am i suppose to find Q1 and Q1 for the 3rd and 4th event? Isn't it just 0? Cause it seems like the temperatures just stayed constant. I'm not entirely sure...

Homework Statement The initial state of 0.1 mol of an ideal monatomic gas is P0=32 Pa and v0=8m3. The final state is P1=1 Pa and V1=64m3. Suppose that the gas undergoes a process along a straight line joining these two states with an equation P=aV+b, where a =31/56 and b=255/7. Plot this...

Homework Statement (a) Deduce from the thermodynamics identities: ##c_v=(\frac {\partial u}{\partial T})_n=T(\frac{\partial s}{\partial T})_n## and equations: ##f(ε)=\frac {1}{e^{ε-μ/k_BT}+1}## and ##u=\int \frac{1}{4π^3}ε(k)f(ε(k)) \, {d \vec k}##...

Long time no see, PhysicsForums. Nevertheless, I have gotten myself into a statistical mechanics class where the prof is pretty brutal and while I can usually manage, this problem finally has me stumped. I'd like to be nudged in the right direction, not outright given the answer if possible. I...

Homework Statement I don`t know if the image will show so I`m also adding a link to the image of the problem. This problem is a modification my professor made to the one in the link below(*), he changed the rigid diathermic partition into a movable partition. I`m supposed to find the...

MODERATOR'S NOTE: NO TEMPLATE BECAUSE THREAD WAS ORIGINALLY POSTED IN A NON-HOMEWORK FORUM A monoatomic gas is present i n cylinder if its volume increase from 100cm3 to 200cm3 at constant pressure 1*10^5 what is change in internal energy. I tried to solve it but couldn't. I tried to solve it...

Hi all, I am trying to learn more about this field. Whether you work or have worked in this area or not, I would like to know where Soft Matter is going in terms of theory and applications. Thanks, A.D. *I apologize in advance if there are already many threads specifically addressing this...

Homework Statement I really don't know if I'm in the right subforum... I've started reading this text on statistical mechanics from MIT, but I'm stuck on page 2. Here's the statement: Let the equilibrium state of systems A, B, and C be described by the coordinates {A1, A2,· · ·}, {B1, B2,·...

Hello - I am wondering abut the meaning of chemical activity. Most definitions are something along the lines of "effective concentration," which is fine until you have a real concentration in a lab, and you don't know if you need to calculate the concentration or "effective" concentration of the...

Does use of solar panels or other radiation capturing technologies in itself warm the earth? Since solar energy is radiated partially back to space, then, when a portion of it is captured and converted to electricity which performs work and rseleases heat (e.g. in transmission lines) it would...