Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also in other complex fields such as meteorology.
Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Nicolas Léonard Sadi Carnot (1824) who believed that engine efficiency was the key that could help France win the Napoleonic Wars. Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency."
The initial application of thermodynamics to mechanical heat engines was quickly extended to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged. Statistical thermodynamics, or statistical mechanics, concerns itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a purely mathematical approach in an axiomatic formulation, a description often referred to as geometrical thermodynamics.
Homework Statement
A pure substance is placed into two containers of the same volume. Container 1 has twice the mass of pure substance of Container 2. After the containers are shut and both reach thermal equilibrium with the surroundings, what do we know about:
a) the pressure of Container 1...
My question is: according to Carnot cycle, the maximum efficiency of a heat engine is given by 1 - T2/T1, where T2 is the temperature of the cold source and T1 the temperature of the hot source. So, accordingly, as higher T2 is for a same T1, lowest is the efficiency of the engine. But, the...
Hi guys,
i just discovered this forum and this is my first post so apologies if i made any mistake with the how I am suppose to structure a thread. but nontheless any help would be greatly appreciated!
cheers
1. Homework Statement
4. A 250mm diameter insulated cylinder (see figure below) is...
Hi everyone,
I have been looking at Carnot heat engines in a bid to better understand entropy, and I can't figure out how it actually does work. Why does the piston move?
In some diagrams I have seen weights being removed from the piston, reducing the pressure at constant temperature and...
In Principles of General Thermodynamics, Hatsopoulus and Keenan (p 442) make the following claim:
What, however, would be some physical examples of such a system?
What is the role of Quantum Mechanics and Thermodynamics in solar cell operation?
Is quantum mechanics the photovolatic effect, and thermodynamics the cell efficiency?
I'm currently reading thermodynamics which is only the second volume of all the physics course that I'm planning to read. So for the math in it is just killing me literally. Mechanics was relatively easy but this subject is just too freaking hard. All these partial differential equations and...
Hi!
I'm a junior in high school studying for the IPhO and I've started learning thermodynamics as part of my preparation. I have a guide to the exam that says things like this will be tested:
Carnot engine
Kirchhoff's law
Wien's law
Stefan's law
Stefan-Boltzmann law
Newton's law of cooling...
Homework Statement
Show that (du/dv)T = T(dp/dt)v - p
Homework Equations
Using Tds = du + pdv and a Maxwell relation
The Attempt at a Solution
I've solved the problem, but I'm not entirely sure my method is correct.
Tds = du + pdv ---> du = Tds - Pdv
- Using dF=(dF/dx)ydx +(dF/dy)xdy...
What I know: Below link is about Torricelli's law. Velocity of liquid coming out of bottom of the tank i.e comes after using Bernoulli's equation square root of (2*g*h*) where "h" is height of fluid in the container and "g" is acceleration due to gravity...
I guess there would be no flow in case 2; case 3 seems easy to me applying fluid mechanics principle; flow will be 1 to 2. But I doubt case 1; it is not in thermal equilibrium ? Pls help
Hi all, I'm working through a derivation of the general relationship between Cp and Cv and there's one point which is confusing me.
I understand that
and
and that this implies the following:
but isn't this equal to 0? Shouldn't the two partial derivatives on the right...
Why is is true that for a given system, if I fix the volume and increase the temperature, you'd expect the occupancy of the energy levels to change, but not the levels themselves?
Can I think of this in terms of the fact that the boundary conditions for the solution of the TISE are fixed, such...
Homework Statement
Please see the attached image
Homework Equations
pv=nRTThe Attempt at a Solution
i don't know how to calculate the work done by the gas in the question and i calculated the change in internal energy.
NO TEMPLATE---MISPLACED HOMEWORK
So it seems like a pretty simple question, and in all likelihood it is, but my lecturer somehow managed to miss this bit in his lecture notes.
A heat engine operates between 500K and 300K with 20% of the efficiency of Carnot engine operating between the same...
Homework Statement
A 10.0 g sample of solid platinum is placed in a large, sealed vessel at a sufficiently low pressure that the platinum is able to sublimate directly to a gas. Some thermodynamic properties of platinum at low pressure are given in the following table.
Molar mass, M - 195...
Homework Statement
two cubic ft, of air at 85 f and 13.9 psi, compress to 115 psi.
What is the final temp, the work, the internal energy "delta u", and Q
Homework Equations
well i don't have any equations, i am asking for the equations
The Attempt at a Solution
i don't know how to approach to...
Homework Statement
Hello, new here! I have a question regarding reversible or irreversible expansions in regards to figuring which equation is needed to figure out work, W. For starters, here is the question:
One mole of an ideal monatomic gas is expanded from an initial state of 3 atm and 500...
Homework Statement
A 3.20 g lead bullet at 28.0°C is fired at a speed of 210 m/s into a large block of ice at 0°C, in which it becomes embedded. What mass of ice melts (g)?
Homework Equations
I thought that the KE of the bullet would be transferred into heatThe Attempt at a Solution
I used...
Homework Statement
Steam, at 15 bar and 280oC, enters a nozzle with an initial velocity of 125 m/s. The steam enthalpy at the exit section is 2800 kJ/kg and the heat loss is 25 kJ/kg. What is the exit steam velocity?.
Homework Equations
1)Qin - Qout = m [h2-h1+((c22-c12))/2]
2)h = Pv + u...
Homework Statement
I.The gas is heated at constant pressure until the volume is 4.4L at point B
II. The gas is cooled at constant volume until the pressure decreases to 1.2 atm
III. The gas undergoes an isothermal compression back to point A
a) Find the temperature at Point A,B,C
b) Find the...
Homework Statement
You add 50 g of steam at 150 degrees centigrade to 50 g of ice at negative five degrees centigrade. What is the final temperature?
Homework Equations
Q = mLfv
Q = mcΔT
The Attempt at a Solution
Qg = Ql
Q1 + Q2 = -Q3 - Q4
mLf + mcΔT = -mLv + mcΔT [ΔT will be negative, making...
When I leave a closed half full bottle of water overnight, the next morning I find condensation on the inside walls of the bottle BUT! Only where sun light has reached it! I thought this was widely known and easy to explain, but I've been looking on the Internet for a while and haven't found a...
Homework Statement
[/B]
An insulated cylinder containing water has a piston held by a pin. The water is initially saturated vapour at 65°C and a volume of 5L. The piston has a total mass of 10kg, its area is 0.003 m^2 and the atmospheric pressure is 100kPa. The pin is then released, allowing...
The thermal efficiency of a reversible heat engine is solely a function of the temperature of the two reservoirs.
η = f(θH,θC) = 1 - (QC/QH)
(QC/QH) = 1 - f(θH,θC)
(QC/QH) = Ψ(θH,θC)
The simplest function that can be used is T1/T2
(QC/QH) = T1/T2
In order to define the Kelvin scale we assign a...
Homework Statement
Freezing of water at 273 K and 1 atm
which of the following is true for the above thermodynamics process
p) q=0
q)w=0
r)ΔSsys<0
s)ΔU=0
t)ΔG=0
Homework Equations
none[/B]The Attempt at a Solution
[/B]
i got r, s ,t
since the reaction happens at constant...
Homework Statement
A 10 L truck engine has a volumetric efficiency of 100%. It has a turbocharger which increased the mass flow of air and its pressure by a factor of 2 when the engine is running at 4300 rpm. Find the turbocharger rpm, efficiency, and the temperature of the air leaving the...
qrev/T = ΔS
here what does ΔS signify?does it mean change in entropy of system or surroundings?
how is entropy of system,surrounding and universe related to each other and which entropy is used in gibbs free energy equation?
Hello
I am confused with the energy conservation equation in thermodynamics.
Is it U2 - U1 = Q - W ? This is what most books say.
Or is it H2 - H1 = Q - W ?
Which should I use to solve problems? For example we have a gas with U1 and P1V1 (which makes H1). After a process, we have Q...
Hello,
I would expect the heating of an elastic material upon sudden elastic compression to be given simply by the first law of thermodynamics, i.e. Delta Q=Delta U + P Delta V where P is constant since the compression is applied suddenly as in a square-wave pressure pulse (this is equivalent...
I have heard (read) much debate over the fundamental problems with white holes, mainly that they violate Thermodynamics by increasing entropy. However, I have also read that a black hole bends space-time enough to "connect" somewhere else as an Einstein-Rosen Bridge. So if the exact same event...
Homework Statement
Suppose you walk into a sauna that has an ambient temperature of 57.0°C. Calculate the rate of heat transfer to you by radiation given your skin temperature is 37.0°C, the emissivity of skin is 0.95, and the surface area of your body is 1.60 m2.
I solved this first part and...
Too much confusion in my head about these concepts...
Is every reversible process quasi static? If not, what are some examples?
If process is irreversible then it doesn't need to be non quasi-static, I understand that. (eg. free expansion of the gas)
Can irreversible process be quasi static...
For a system modelling a soap bubble, the differential work done is now given by:
dW = −pdV + γdA, where γ is the surface tension and A the area. Compute new differential expressions for the potentials U, H, F, G. What are the new natural variables in each case? Are there any new Maxwell...
A one-dimensional polymer molecule (rubber) is chain of N links of the same length a, the links can go either forward or backward but always stay parallel to the x axis. If one denotes the coordinates of the joints are ${x_0, x_1, . . . , x_N}$ , then $|x_n − x_{n+1}| = a$. The energy of the...
If I have a closed system where mass is conserved, what constraint will this bring on the system in terms of infinitesimal quantities. What conclusions can I then draw about the phases at this kind of equilibrium? Suppose we had an isovolumic, isothermal change, how would I have to alter my...
Hi! I'm new to the forums, so I apologize in advance if I'm posting my question in the wrong section. I'm studying thermodynamics right now, and I came across this sentence from my book:
Homework Statement
"When energy is added to a system and there is no change in the kinetic or potential...
Homework Statement
I'm doing a class on thermodynamics and energy and well there's this chapter about pure substances and subcooled liquids, saturated liquids, superheated, etc. stuff like that.
The chapter begins by showing a piston-cylinder in an initial state containing liquid water and a...
Let's consider two spherical blackbodies at two foci inside an ellipsoidal heat-reflecting shell. Consider the situation that they both have different radii and that their temperatures are such that they emit the same power. Thus, the surface power flux density of each is inversely proportional...
Homework Statement
1.
A gas expands as shown in the graph. If the heat taken in during this process is 1.02 × 10^6 J, the change in internal energy of the gas (in J) is
2.
One mole of an ideal gas is held at a constant pressure of 1 atm. Find the change in volume if the temperature changes by...
Homework Statement
Two kilograms of air at 5 bar, 350 K, and 5 kg of carbon monoxide, initially at 4 bar, 450 K, are confined to opposite sides of a rigid, well-insulated container by a partition. The partition is free to move and allows conduction from one gas to the other without energy...
Homework Statement
How do we obtain:
w = q - Δh
Homework Equations
The Attempt at a Solution
If you neglect the second half of the SFEE and simplify we get:
What is the next step from the last line in the above image to
w = q - Δh
I mean dw/dt = dq/dt - Δh
so if we multiply by dt we...
Homework Statement
I have a question regarding heat engines that cropped up whilst I was doing a practice question. I will summarise the results I obtained for the previous parts of the question so as to save your time. The highlighted parts of the image are where I am having some issues.
I...
How would I calculate the rate that water would boil off? I've done a lot of looking into and found an equation but it doesn't seem quite right. What I found states that the KJ/h delivered to the water divided by the latent heat energy gives you the amount of water that will boil off. I tried...
I am studying for a thermo exam, and one of the problems I am doing deals with adiabatic expansion of a piston in a cylinder. When solving for work, the solution guide uses m*Cv*(T2-T1). I don't understand why they know how to use Cv instead of Cp. The pressure changes, so obviously you wouldn't...
Homework Statement
The thermal dissociation equilibrium of CaCO3 (s) is studied under different conditions.
CaCO3 ⇔ CaO (s) + CO2 (g)
For this equilibrium, the correct statement(s) is (are)
(A) ΔH is dependent on T
(B) Keq is independent of the initial amount of CaCO3
(C) Keq is dependent on...
Hello!
This is an old problem from the Estonian-Finnish open physics olympiad (2013) and I hope you will be able to lend me some help.
1. Homework Statement
Sun-rays are focused with a lens of diameter d = 10 cm and focal length f = 7 cm to a black thin plate. Behind the plate is a mirror...
Homework Statement
A column of water contains fine metal particles of radius 20 nm, which are in thermal equilibrium at 25°C. If there are 1000 such particles per unit volume at a given height h0 in the water column, how many particles would be found in the same volume 1.0 mm higher than h0...
THIS WAS MOVED FROM ANOTHER FORUM, SO THERE IS NO TEMPLATE. HOWEVER, THE OP DID SHOW SOME EFFORT
Hello, I have been having troubles beginning these two problems given for exam prep. Was wondering if anyone could give guidance on where to begin.
Problem 1:
A cylinder with adiabatically...