What is Thermodyamics: Definition and 267 Discussions

Homework Statement Show that for a gas obeying the van der Waals equation ##\left(P+\frac{a}{v^2}\right)(v-b)=RT##, with ##c_v## a function of ##T## only, an equation for an adiabatic process is $$T(v-b)^{R/c_v}=constant$$ Homework Equations ##TdS=c_vdT+T\left(\frac{\partial P}{\partial...

Hello, I am working on the following problem: Homework Statement -------------------------------------------------------------------------------------- During the modifications in the process you are working on, your direct boss is interest in replacing a few equipment for new ones in order to...

Homework Statement a copper pot's radius is 12 cm, the thickness is 5 mm. It is placed on the stove for boiling, if the temperature of the stove is 115 oC while the water is 100 oC. How much of water that evaporates per minute Homework Equations ΔQ/Δt = (A)(k)(ΔT) / (L) Q=mcΔT The Attempt...

Homework Statement A silicon electric circuit is 23 mg, when electricity flows through the circuit rising the energy by 7.4 mW but this circuit wasn't design for heat ventilation. Find the rate of how much the temperature is rising per second ( ΔT/Δt ) The specific heat of silicon is 705...

1. Can I say Carnot efficiency of a heat engine is always smaller than 100 because the temperature of cold reservoir is always greater than 0 Kelvin? 2. Is the following analogy correct to describe the relation between temperature and heat energy? "Heat energy affects internal energy which...

If I have a tank of volume V, pressure P, and temperature T, what is the most effective way to determine the volume flow rate if I were to suddenly allow the air to discharge through a hose? My first thought was that I could use Boyle's Law to determine the compressed volume of air in the tank...

Homework Statement An expandable cylinder has its top connected to a spring of constant 2000 N/m. The cylinder is filled with 5L of gas with the spring relaxed at a pressure of 1 atmosphere and a temperature of 20C. If the lid has a cross-sectional area of 0.01m2 and negligible mass, how high...

In a trasformation in which P=costant, but internal pressure is different from external pressure, ΔH=Q? I'm asking this question because I know that Q=ΔU+PΔV (where P is the external pressure) and H=U+PV (where P is the sistem pression, so the internal pressure) Am I right?

For a business project, I'm looking into the viability of a greenhouse situated in Canada's far northern town of Iqaluit. The problem is how to mathematically simulate the internal air temperature of the greenhouse. What I already have are detailed 3D renderings of the greenhouse as well as all...

Doing my undergrad thesis on a ramjet and am confused about scramjets. A ramjet's diffuser slows down supersonic inlet flow to low subsonic to allow combustion. But a scramjet's diffuser first slows the flow down, then speeds it back up in the "diverging" section for supersonic combustion. Why...

I've recently been reading a bit into the thermalisation of a system of particles and I'm unsure on a couple of concepts. Firstly, if a system of particles are out of mutual thermal equilibrium, does this essentially correspond to the particles in the system having randomly distributed momenta...

According to Kirchoff $$e=J(T,f)A$$ ##e## is the power emitted and ##A## is the power absorbed If ##E## is the power supplied, can I say that $$e=E-A$$

I came up with a basic doubt on heat exchange. Consider this example situation. A cube of ice of mass ##m## and at temperature ##\theta <0°C## is put in contact with a resevoir exactly at the temperature ##T=0°C##. The question is: does the ice melts, i.e. does the ice pass to liquid state? Or...

I'm confused on the efficiency of a Thermal engine in the case it is reversible or not reversible, in particular where the ideal gas follows isochoric or isobaric processes. Infact during isochoric and isobaric processes $$Q_{isochoric}=n c_v \Delta T$$ $$Q_{isobaric}=n c_p \Delta T$$ So the...

The thermal engine efficiency is defined as $$\eta = \frac{W_{\mathrm{produced}}}{Q_{\mathrm{absorbed}}}\tag{1}$$ A more general definition of efficiency (not only for thermal machines is) $$\eta = \frac{\mathrm{Work \, produced}}{\mathrm{Energy \, absorbed}}\tag{2}$$ But suppose that, in one...

In a adiabatic process (not necessarily reversible) from ##V_a## to ##V_b## the work can be written as $$W=\frac{p_aV_a-p_bV_b}{\gamma-1}$$ Where ##\gamma= \frac{c_p}{c_v}## Suppose that the adiabatic process in question (again, not necessarily reversible, so ##pV^{\gamma}## can also not be...

I came up with a doubt regarding isochoric irreversible processes. Is it always true that, for any isochoric process, reversible or not, the work exchanged by the system is zero and the heat exchanged is ##Q=\Delta U##? I'm asking this because, in a exercise on thermodynamics trasformations of...

Hi Physics Forums, I'm wondering if a distillation column is limited by the carnot efficiency and, if so, how this limitation can be used to determine the maximum efficiency of a distillation column with particular hot and cold side temperatures. A distillation column has a hot and cold side...

What is the change in entropy of thermodynamic environment if it changes its temperature during the process and the process is not reversible? I'm slightly confused because, on the one side, in that case ##\Delta S_{gas} \neq -\Delta S_{surroundings}##, since ##\Delta S_{universe} >0## but on...

Homework Statement The following data refer to an electrically operated refrigerator: - Efficiency : ## \xi = 2.4## - Temperature inside: ##T_i = -9 ° C ## - Temperature of the radiator ## T_r = 40 °C ## - Room temperature: ## T_s = 35 °C## - Total surface of walls: ## A = 3.2 m ^ 2 ## -...

Homework Statement The figure at the bottom shows a cylindrical tank of diameter D with a moveable 3.00-kg circular disk sitting on top. The disk seals in the gas inside but is able to move without friction. The gas inside is at temperature T. The height of the disk is initially at h = 4.00 m...

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...

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...

I am trying to find an expression for the average Nusselt number corresponding to heat transfer from an isothermal disk. Given: ShD≡hm(r)D/DAB=Sho[1 + a (r/ro)n] (1) Sho=hm(r=0)D/DAB=0.814ReD1/2Sc0.36 (2) Relevant equations: Average nusselt number is defined as Nuav=havD/k where k...

I have some doubts on entropy change of certain simple process. Can you check if these statements are correct? This is what I know: For a reversible adiabatic process, $$\Delta Q=0$$. $$\Delta S_{system}=\frac{\Delta Q}{T}=0$$. Since the system does not alter the surroundings, ##\Delta...

Homework Statement A spacecraft is protected from the Sun’s radiation by a planar baffle whose size is much greater than that of the spacecraft itself. The baffle is aligned perpendicular to the direction of the Sun. Show that the equilibrium temperature of the baffle is...

I was debating on another forum how hot a heat source in a cartoon would have had to be to cause a temperature increase in the atmosphere. In a cartoon, I found a scene in which a "fireball" (not really fire) heats the air to create a warm front immediately, clashing with an ice beam that...

A) The active element of a laser is made of a glass rod 25.0 cm long and 1.40 cm in diameter. Assume the average coefficient of linear expansion of the glass is equal to9.00 10-6 (°C)−1. The temperature of the rod increases by 64.0°C. i) What is the increase in length? I worked this out to be...

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...

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...

I have attached two images from my textbook one of which is a diagram and the other a paragraph with which I am having problems. The last sentence mentions that due to violation of 2nd law we cannot convert all the heat to work in this thermodynamic cycle. However what is preventing the carnot...

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...

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...

Homework Statement We are given a paramagnetic system of N distinguishable particles with 1/2 spin where we use N variables s_k each binary with possible values of ±1 where the total energy of the system is known as: \epsilon(s) = -\mu H \sum_{k=1}^{N} s_k where \mu is the magnetic moment...

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...

Two Thermally insulated cylinders, A and B, of equal volume, both equipped with pistons, are connected by a valve. Initially A has its piston fully withdrawn and contains a perfect monatomic gas at temperature T, while B has its piston fully inserted, and the valve is closed. Calculate the final...

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...

I have derived a few equations to determine temp distribution through pipe wall in subsea conditions. However I am finding it difficult to determine what the wall temperature will be. I need to know and use this temperature to further my analysis. As of now I know the following parameters...

Homework Statement An ideal gas enclosed in a vertical cylindrical container supports a freely moving piston of mass M. The piston and cylinder have equal cross sectional area A. When the piston is in equilibrium, the volume of the gas is V0 and its pressure is P0. The piston is slightly...

I have read that osmosis " works like a machine ". It lifts weight ( this is obvious ) on the expense of thermal energy. Does anyone has any thoughts about how it consumes thermal energy? Thank you in advance.

Homework Statement Here is the problem: An inventor claims to have developed a heat pump that provides a 180 kW heating effect for a 293 K household while only consuming 70 kW of power and using a heat source at 273 K. Can this claim be possible? Homework Equations COP of heat pump = Qh/W COP...

Homework Statement Which of the following are not extensive functions: S[1] = (N/V)[S[0]+[C][v] ln(T) + R ln(V)] S = (N)[S[0]+[C][v] ln(T) + R ln(V/N)] S[3] = ([N])[S[0]+[C][v] ln(T) + R ln(V/N)] 2. Homework Equations I'm not really sure how to approach this problem. The definition that I...

Homework Statement 1. (a) From the following data, 2 Cu (s) + S (s) Cu2S (g) ∆rH° = - 79.5 kJ mol-1 S (s) + O2(g) SO2 (g) ∆rH° = - 296.8 kJ mol-1 Cu2S (s) + 2 O2(g) 2CuO (s) + SO2(g) ∆rH° = - 527.5 kJ mol-1 Determine ∆rH° for Cu(s) + ½ O2 (g) CuO (s) at 298 K (b) Given the following Cp / (J...

Homework Statement A sample consisting of one mole of a diatomic perfect gas is heated from 25 °C to 200 °C at constant volume. Calculate q, w, ΔU and ΔH for the process, given that Cv = 23.02 J K-1 mol-1 . Homework Equations Im studying for mid terms and i have no lecture notes on diatomic...

Homework Statement "Determine the polytropic process index 'n' from the initial and final condition parameters of the air (gas) in the air compressor cylinder." Im struggling with this question on my thermodynamics coursework and was wondering if anyone could help me out a little bit...

This is a thermodynamics question.I am a beginner and know only algebra.Here's a description.A cylinder full of CO2 gas at 670 psi is compressed by a piston.At the far end of the cylinder is a pipe,through which the CO2 gas flows to push a piston into another cylinder.At one third of the stroke...

If for two reversible processes we have the same internal energy change, if work done is maximum for one, is heat transfer minimum and vice versa? The logic that I use is that since dU=dQ+dW, for constant dU if dW is more for one, heat transfer dQ is less and vice versa just to keep the sum...

Homework Statement A system possesses three energy levels $$E_1=\varepsilon$$ $$E_2=2\varepsilon$$ $$E_3=3\varepsilon$$ with degeneracies $$g(E_1)=g(E_3)=1$$ $$g(E_2)=2$$. Find the heat capacity of the system. Homework Equations $$\beta=\frac{1}{kT}$$ $$Z=\sum_i g_ie^{-\beta \varepsilon_i} \...

Homework Statement Hellooo, so this is the question that i have: A 0.5-m3 rigid tank initially contained a saturated liquid-vapor mixture of water at 140 °C is now heated until the mixture reaches the critical state. Determine the mass and the volume of liquid before the heating process...

My textbook says that net rate of heat transfer due to radiation is εσA(T^4-To^4) but i couldn't understand it. Rate of emission is εσAT^4 and rate of absorption is aσATo^4 so net rate of heat transfer must be εσAT^4-aσATo^4(where T is the temperature of body and To is the temperature of...