Gas Definition and 1000 Threads

I am a beginning graduate student and I've been assigned a paper which uses landau levels for 3d fermionic gas in uniform background magnetic field. I am having trouble finding a proper source which deals with solution of dirac equation in such a case. With the two papers that i have found which...

Please, i need help

The image above is the solution posted by the book. I can follow the reasoning that has been used, but i have a trouble particularly at the first equation itself. Why should $$n = 2 \rho / m_{H} $$ instead of $$n = \rho / (2m_{H})$$, since the mass os a molecule of hydrogen is two times the...

Hi, I’m looking for formula to find the energy stored in a compressed gas for non ideal gases, for example, argon. The formula should also include the thermal energy caused by compression. Thank you in advance.

As we know, dipole can be only arranged either parallel or anti-parallel with respect to applied magnetic field ## \vec{H} ## if we are to use quantum mechanical description, then parallel magnetic dipoles will have energy ## \mu H ## and anti-parallel magnetic dipoles have energy ## -\mu H##...

Hi, Originally, the absolute temperature was thought to be around -273 Celsius around 1750 and it was the result extrapolation of of ideal gas law as shown below. I find it hard to phrase my question. But the question is how come they were so confident that the relationship between the volume...

I'm building a gas supply system that will dump half the contents of a compressed gas cylinder of nitrogen in 10 minutes. I need to ensure the output delivery pressure doesn't fall below a certain limit because of cooling during the gas expansion. If the cooling effect is excessive, I will...

Question: Answer: In the third last line of working, I do not understand why the pressure variable is changing? Shouldn't pressure remain constant and only the Volume change?

Hello my friends. I would like to know if you guys are aware of some site or paper that provides informations about gas. That is, i would like to know the energy band in which the ionization of a gas is high, and also the energy in which multiple scatter is high. The gas need to be Argon of Neon.

I assume the system starts from rest so the total initial momentum is zero. Let: M = mass of trolley + cylinder m = initial mass of oxygen Δm = mass of ejected oxygen u = speed of ejected oxygen Conservation of momentum: 0 = (M + m - Δm) . vmax - u . Δm 1) Is my equation correct? 2) I...

Hi, I have to found the number of microstates for a gas of N spheres of radius r and volume v in box taking into account the reduced volume after each sphere. V sphere << V box. I'm struggling to find the microstates in general. I don't see how to find the number of microstates without knowing...

Is regular grade gas detrimental to a car’s engine?

Hi, this is a question from my textbook that I can't quite make sense of. I don't really know where even to begin, to be honest. The only thing I can think of is that the bead is at equilibrium, thus the force of gravity is equal to the pressure exerted by the gas. I don't know where the heat...

Suppose we have a cylinder with one wall guard by a demon. Inside is one gas molecule moving left and right for simplicity. Now we want to closer the wall (compress the gas) without doing work. The job of the demon is push the wall closer when the gas move left and lock the wall when the gas...

A gas with a volume of 8m^3 with a temperature of 400K gets warmed up to 550K with a constant pressure of 200Kpa. How much work has the gas done to the environment? I think i might need to use the ideal gas law for this which is: ( P * V / T = N * K ) Where V is volume, T is temperature and N...

In other words, is there a rotational orientation of each atom in a monatomic gas (and corresponding rotational speed conserving angular momentum) that affects collisions, or does a substance need to have at least 2 atom particles to have the orientation/rotational ability to have particle...

Say there is a gas made up of two gas molecules: Molecule A and Molecule B. Molecule A has a mass: ma and mole fraction: na. Molecule B has a mass: mb and mole fraction: nb. The gas is at thermal equilibrium and has a constant temperature throughout itself (T) everywhere. It is placed in a...

I need help understanding what happens to the gas that is being worked by the piston, in the crank slider. My goal is to produce linear motion on an object up to a certain height and I'm wondering since the slider moves back during the rotation of the crank what happens to the object I'm trying...

Hello, for an instrument I have given the Kvs-Value for water and I want to convert it to gas. Can someone help or explain the calculation? Of course I have the formulas for liquid and for gas KVs-calculation. How do I convert it? Thanks for the help Falko

Hello. I am wondering; which solid at room temperature elements produce oxygen gas when put into a solution of sodium hydroxide? Thanks

If particles are trapped in one half of a massless container by a barrier, and the barrier is removed so that the particles are allowed to expand to fill the whole container, it seems the center of mass would be displaced to the center of the container, whereas before it was located at the...

Following up on a previous discussion: https://www.physicsforums.com/threads/conservation-of-momentum-in-a-closed-system.1009693/post-6570341 An uncontained system of particles interacting only by elastic collision is the same as a gas undergoing free expansion. If, for simplicity, the...

Summary:: How to find gas flow through an orifice that links two vessels at different pressures. Two vessels containing the same gas are linked through an orifice with diameter ##d##. The pressure inside vessel 1 is ##P_1## and the pressure inside vessel 2 is ##P_2##, and let's have...

I was reading around Stirling engines and there's something I am not sure about, can't see a logical explanation. So the ideal gases discussed are hydrogen and helium on account of their higher thermal conductivities. But I am unclear on what motivation there would be to use hydrogen which has...

Hello, I normally get these things working but I am a bit stuck as i don't feel I am getting sensible answers... The problem is simple (!): Q: Model the flow through an orifice with an upstream/supply pressure of 301BarA where the downstream pressure is in the range 1BarA to 301BarA. The...

I'm excitedly close to the end of proofing my latest novel, and as happens, tweaking of passages occurs. In this instance, a fleet of warships travel together in a collective warp space bubble that has inconsistent gravity, especially around the edges. To facilitate shuttle transfers between...

In the fermi gas model, there is assumption that there is a 3D potential well, but there is "energetic degeneration" for each three index "nx, ny, nz". Now the problem is with that image, if there is degeration, for some level En there may be 10 distinctive state with same energy, so there is 20...

So a and b were pretty straightforward. Got stuck on part c. The question says they approximated Van der Waals in first order in a and b. So I started with that by rewriting Van der Waals eqn as ## p = \frac { N \tau } { V - Nb } - \frac {N^2a} {V^2} ## and I then Taylor approximated ## \frac...

The following link states that: "since kT ~ mpv2. A typical velocity dispersion 700 km/s implies T ~ 6 x 107 K from this source alone." How did they get 6*10^7K ? When I try this, using mp = 1.67*10^-27 , k =1.38*10^-23 I end up getting 84 as a final answer, nowhere near 6*10^7. Can anyone...

Hi, reading the interesting Reversible vs Irreversible Gas Compression and Expansion Work insight by @Chestermiller I would like to ask for clarification on some points. In the second bullet at the beginning my understanding is as follows: consider an ideal gas contained in a cylinder...

I read that a kg of gas provides about 13kWh (47.5MJ) of energy and that burning a kg of gas emits about 3.15 kg of CO2. So presumably a gas-powered engine emits 3.15/13 or about .242kg of CO2 per kWh of work, right? According to the EIA, the US electric grid emits about 0.85lb or 0.386kg of...

a) We use the definition of heat transfer in a gas at constant volume: Q = n*C_v*delta_T = (0.01 mol)(12.47 J/mol*K)(40 K) = 4.99 J b) We use the definition of heat transfer in a gas at constant pressure: Q = n*C_p*delta_T = (0.01 mol)(12.47 J/mol*K)(40 K) = 8.31 J c) In both processes delta_U...

This is from Problem 7.45 of Thermal Physics by Daniel Schroeder.

I often see this set up in thermodynamic problems and need clarification on how Newton's Laws are involved for the piston: Gas inside a piston cylinder (1) is heated expanding the gas and raising the piston (initially at rest) to a height (2) in a constant pressure quasi-equilibrium process...

So for a collection of particles each with mass m, the pressure beneath them, ##p(z)## should be higher than the pressure above them ##p(z + \Delta z)##. This is a change in force per unit area (force per unit volume I suppose) times a volume to equate with the gravitational force $$ \frac...

Summary:: Irreversible process required to go from state 1 to state 2 If we start with an ideal gas at state 1 and undergo an isentropic compression, then follow this with an isothermal expansion, we could end up in a state, call it state 2, that has higher temperature, higher pressure, and...

When refrigerant enters the metering device of an air-conditioner, the refrigerant enters the metering device as 100% liquid. When the refrigerant in a straight air-conditioner goes through the metering device, the metering device lowers the pressure of the refrigerant a great deal. The...

So when volume decreases, pressure increases according to Boyle's Gas Law and the ideal Gas Law. In other words, compressing gas into a smaller volume increases the vapor pressure. And also, According to Gay-Lussac's Law and ideal Gas Law, when pressure increases on a gas, temperature also...

Summary:: Proving that entropy change in mixing of gas is positive definite > >An ideal gas is separated by a piston in such a way that the entropy of one prat is## S_1## and that of the other part is ##S_2##. Given that ##S_1>S_2##, if the piston is removed then the total entropy of the...

A container of 0.5l containing 6 moles of CO2 are heated to 200 ° C on is interested in explaining the pressure variations between the pressure of a perfect gas and the actual value measured on a pressure gauge. The coefficients of the real gas a=3.59 [atm l2/mol2-] b=0.0427 [l /mol] indicate...

A photon often travels billions of years (Gyr) through the CMB photon gas (410 photons per cubic centimeter) to reach us. Does it travel freely? Let’s share our thoughts about this. For discussion purpose, let’s assume the photon has a wavelength of 500 nm, close to the peak of the solar...

a) ##P_f=\frac{nRT_f}{V_f}=\frac{nR\frac{T_i}{2}}{2V_0}=\frac{1}{4}\frac{nRT_i}{V_0}=\frac{1}{4}P_i## b) ##Q=\Delta U=nC_V \Delta T=n\frac{5}{2}R(-\frac{T_i}{2})=-\frac{5}{4}nRT_i=-\frac{5}{4}P_i V_0## (##L=0## since the gas expands in a vacuum;Now, (a) and (b) are both correct but not (c), for...

Hey, its that under educated guy again, I hope the mighty big brains can spare me my feelings. Anyways, I saw this toy that levitated a ball of water using nothing but sound waves. So naturally I tried to apply this to a plasma and fusion. Using a inert gas reactor, or a fusor for that matter or...

By using the given relationship that S=a/T --(1) along with the equation ∫ (delta Q rev)/T=∫dS -- (2) I found out that my answer for the value of Q is mc*ln (T2/T1)*a upon equating (1) & (2). But the solution is instead given as Q=a*ln*(T1/T2). I would be grateful if someone would point out...

In private discussions, another member @burian and I have been discussing why, in compression and expansion of a gas, the work can be calculated from ##W=\int{P_{ext}dV}##. We thought it would be of value to open the discussion to the full membership. Burian last asked about: When the...

Solution attempt : Option : I am sure that my work is wrong. But, I must add solution attempt in PF that's why I just added that. How can I solve the problem?

Summary:: Heat capacity for real gas with ideal gas (zero pressure) equation I'm looking at this problem and I'm stuck. I usually question everything but this problem is confusing me. I don't know how they've made the jump from reduced properties (from generalized Cp charts(?)) to...

In all gas turbines air is first compressed using a compressor and then head added in a combustor and finally the hot pressurized air is expanded in nozzles to convert air contained energy to kinetic energy which can be harvested and transferred in the form of thrust or shaft rotation. My...

I was reading a post about the effects of RPM on gas mileage, It was from 2007 so I couldn't reply to it. RPM does make a difference on gas mileage when it comes to overdrives. I had an '82 Buick Riviera with a small block engine with an overdrive and a quadrajet that got 26 MPG on the freeway...