Helium Definition and 389 Threads

Homework Statement a)Helium enters a closed system as a flow of compressed gas at a temperature of 14 K and at pressure p (enthalpy conserved). A fraction α emerges as liquid and the rest as gas at 14 K, both at atmospheric pressure p0. Find an expression for α in terms of the enthalpy H(p) of...

Hi, Reading about different ways to lift a human being, I've come to realize the easiest is simply manipulating density as follows: Denisty of Air at STP: 1.20 kg/m^3 Density of He at STP: 0.000179 kg/m^3 Therefore for every cubic metre (m^3) of air displacement, lift achieved is ~1.2 kg/m^3...

Hi, Wikipedia says CERN uses 100 gallons of superfluid helium 4 to cool its superconducting magnets. Why use superfluid helium 4 (2K) as apposed to regular liquid helium (4.2K). As far as I can see from Internet sources, the helium serves to keep the magnets in order to keep them in a...

Hello, I am learning about Excited states of Helium in my undergrad course. I was wondering if the total spin operator Ŝ is a vector quantity or not. Thanks for your help.

I read an article about a fusion reactor and how its waste product is helium and I am wondering what would happen if for whatever reason we output massive amounts of helium at a rate similar to how much CO2 we produced at our peak CO2 production? This is purely hypothetical so let's say we never...

Calculate the buoyant force (in N) on a 2.00 L helium balloon. Work: Upward is Buoyant Downward is weight due to gravity $$\Sigma F=0$$ $B-mg=0$ $B=mg$ $\rho=m/V$ $m=\rho*V$ $B=\rho_{fluid}*V_{fluid}*g$ I am stuck on $m=\rho*V$. Am I missing something?

I created a model on autodesk inventor of a concept model kite that would stay in high altitudes and take in wind energy through the cone opening. Is there any advice you can give me about the aerodynamics of this model? (There are balloons that provide lift above the wings, and I want the...

Testing Quantum Gravity Johan Hansson, Stephane Francois (Submitted on 19 Oct 2017) The search for a theory of quantum gravity is the most fundamental problem in all of theoretical physics, but there are as yet no experimental results at all to guide this endeavor. What seems to be needed is a...

Homework Statement "Use the simple MO method to show that the He2+ ion is bound"Homework Equations The hamiltonian for this system is; H=-(ħ2/2m)∇2 -2ke2[∑3i=11/riB+∑3i=11/riB-2/RAB] And as far as I know, the total wave function sould be; ψ = φ1φ2φ3 ... φn , n is the number of electrons and...

Homework Statement A cylinder is fitted with a piston, and the cylinder contains helium gas. The sides of the cylinder are adiabatic, impermeable, and rigid, but the bottom of the cylinder is thermally conductive, permeable to helium, and rigid. Through this permeable wall the system is in...

in the beginning the big bang only created hydrogen and helium. why is that? was there just not enough time to create heavier elements or is there another reason? thx.

My question is the following one: If i have the first excited state of helium, the possibilities for the two electrons are : 1s+,2s+ , 1s+2s-, 1s-,2s- and 1s-,2s+ , where + and - denotes spin up and down. If I use the slater's determinant to generate antisymmetric states, I get : $$|u1> =...

Homework Statement Homework Equations Given in the above picture The Attempt at a Solution I have tried to rearrange the relationship between P and R to gain an expression for R, in terms of P. I subbed that into the expression for E and attempted to differentiate. I ended up with this...

Homework Statement 2. Homework Equations are given in the above picture 3. The attempt at the solution In part a) I simply rearranged the other expressions given and subbed them into the relationship for relative velocity and came out with Vns= Qdot/ρsT(1- ρn/ρs).Then in part b) I started by...

How much helium would a gas cooled reactor require for startup and loss replacement? Would helium's scarcity pose a major obstacle to widespread or long term adoption of it as a coolant for nuclear reactors?

If tokamaks were to be run continuously, somehow, then fusion would produce a lot of helium. But since the charge to mass ratio of helium is exactly the same as deuterium, both of them behave almost exactly he same in electric or magnetic fields. And tritium on the other hand has a lower charge...

I was looking at grotrian diagrams for helium and I see that there is no splitting of energy levels due to spin-orbit coupling. In my book it is said that spin-orbit coupling in helium is small and can be neglected but no further explanation is given. At the same time we do spin-spin coupling...

Scientists created Na2He in a diamond anvil cell. It is stable only above 113 GPa - but it forms at temperatures up to 1500 K, it is not something exotic that breaks as soon as you look at it. Na2He is a crystal with an unusual type of bond - it does not have regular bonds, but it has electrons...

I'm about to do an experiment on second sound in superfluid helium. Reading the lab manual it says we will generate it by putting a heater into the fluid and then passed an AC current through it. What we are going to measure is apparently the 'normal fluid fraction', which I guess under the two...

Why does helium lose enthalpy faster when cooled at a high constant pressure? Thank you.

Homework Statement the relative concentration by mass of helium at 3 minutes after the big bang is 2-5 parts per 100,000. If you had 1 kilogram of the normal matter from the universe at a time 3 minutes after the big bang, how much of it would be normal helium nuclei? Homework EquationsThe...

Homework Statement An excited hydrogen atom can emit photons of various wavelengths. a) What is the maximum wavelength of the Balmer series (in nm) (5pt) b) What is the minimum wavelength of the Balmer series (in nm) (5pt) c) Corresponding to part b), what is the kinetic energy of the recoil...

I thought this could be explained as follows: a singlet state is one with ##S=0##. Electrons have spin ##\frac{1}{2}## or ##\frac{-1}{2}##, and in the ##1s^2## state there are two electrons. For it to be a triplet state both electrons would have to be spin ##\frac{1}{2}## which isn't allowed, by...

Homework Statement What potential difference is needed to give a helium nucleus (Q = 3.2 × 10-19 C) 50 keV of kinetic energy? Homework Equations V=U/Q 3.2 × 10-19 C = 2e The Attempt at a Solution I was quite sure I had the right answer but it keeps saying I'm wrong? V = (50*10^3 eV) / 2e =...

If a Helium ion He+ collides with a diamond wafer surface, an insulator, does the Helium ion, at 25 deg C, will the ion lose it's charge by gaining an electron from the insulative surface or does the ion have an elastic collision with no net energy loss or gain?

Trying to accomplish a monte carlo simulation on the condensed state of 4He, yet I am in my sophomore year and know only a bit of quantum statistical physics. Is there any documentations recommended for beginners to the algorithm applied to 4He? I've found some but they are not friendly to...

Dear all, I have read and heard about helium prices increasing in the future, I was wondering several things. Would it be a good idea to buy and stockpile helium now and keep it for a long time so that I could potentially profit in the future? How do I actually store large amounts of helium...

Hello here is a schematic of the problem: http://imgur.com/CgcybVT A stream of helium gas will be used to carry aerosolized particles. I am assuming conservation of mass (and mass flow) The mission is to find the exit stream velocity of the gas. For the time being, i am assuming the weight...

Homework Statement An aluminum rod 0.500 m in length and with a cross-sectional area of 2.60 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at340 K. (Aluminum has thermal conductivity of 3,100 W/m · K at 4.20 K; ignore its temperature...

There was once hype about mining this on the moon. Still a thing being considered?

Hello everyone, Following Buoyancy formula, how much helium is required to help someone with 80 kg weight against gravity? While the Buoyancy depends on volume, what happens if we compress helium? Thank you in advance. Regards, Behrouz

Homework Statement A clown at a birthday party has brought along a helium cylinder, with which he intends to fill balloons. When full, each balloon contains 0.00260 m3 of helium at an absolute pressure of 1.10 x 105 Pa. The cylinder contains helium at an absolute pressure of 1.80 x 105 Pa and...

Homework Statement The first excited state of the helium atom lies at an energy 19.82 eV above the ground state. If this excited state is three-fold degenerate while the ground state is non-degenerate, find the relative populations of the first excited and the ground states for helium gas in...

I thought this was pretty cool: www.youtube.com/watch?v=sKOlfR5OcB4 You can skip about the first 2 minutes, which are just the credits and some footage of them transferring some fluid. Nice concrete demonstration of various fun stuff such as superfluidity and second sound.

Say we have a Helium atom with the first electron in 1s orbital and second electron in 2s orbital, and if these electrons have parallel spin so that the total spin of the system is S=1, then is this a triplet or a singlet state? According to LS coupling, multiplicity is defined as: 2S+1 (if...

I have this project in school for settlement on moon. I have this idea that the large quantities of He 3 on moon could be extracted by heating the regolith at 700 degrees celsius and then could be taken to a reactor in which He 3 could be fused with Deuterium or itself. The heat produced could...

Homework Statement What is the Vrms, in meters per second, for helium atoms at 4.8 K? (which is close to the point of liquefaction) Homework Equations Vrms= √(3RT)/(M) The Attempt at a Solution R=3.145 T= I think its 4.15 Kelvin? based on the point of liquefaction of helium being -269°C...

I have this formula "E= 1/2 mv^2" which I don't fully understand. Also, I don't have the values for helium's mass and velocity.

Homework Statement A helium balloon of mass 0.2kg and volume 1m3 is attached to a long thin rope of mass density 1g/m. The coils of rope lay flat on the ground, so that as the balloon moves up the rope unwinds without resistance. How high will the balloon rise? Air density = 1.204kg/m3 a)...

why we the alpha particle is taken as helium and beta as electron ? and what about gamma particle ? what is that? My 2nd question is that during alpha decay and beta decay there is decrease of 2 units in atomic number and one unit increase respectively ? what happen in gamma decay ?

Dear PF Forum, Perhaps just yes/no answer would suffice. It's just out of curiosity and I can't find it on web. Or there are no answers :smile: Are there no noble gas compound? There are CH4, CO2, H2, O2 even O3 What about Helium, Argon, Neon? Are there really no compound with noble gas? If...

Hi. I am wondering about this. I have been able to find many graphs showing what the atomic orbitals look like for hydrogen, but nothing for more complex atoms, like helium. Why is this? Now I know the Schrodinger equation for helium cannot be solved exactly, but you don't need an exact...

Homework Statement A piston-cylinder device initially contains 0.5 m^3 of helium gas at 150 kPa and 20°C.Helium is now compressed in a poytropic process(Pv^n = constant) to 400 kPa and 140°C. Determine the entropy change of helium and whether this process is reversible, irreversible, or...

I'm using Chaisson'/McMillan's "Astronomy, a Beginner's Guide to the Universe"/7th Edition In Chapter 7, it describes the gas giants, and says that Jupiter, Uranus, and Neptune all have "86% Hydrogen, 14% Helium" in their atmospheres, while Saturn has about 92% hydrogen, and 7% Helium, in its...

Homework Statement a) Explain qualitatively why the energy required to remove one electron from the ground state of the helium atom is much larger than that in hydrogen, while for other states the hydrogenic value is quite a good approximation, e.g. the 1s2s levels in helium have energies very...

I'm curious, why does Helium-3 fission into H-3 and H upon neutron absorption? Surely the He-4 nucleus configuration is more stable? I get that the energy release may be what splits the nucleus, because it releases quite a lot of energy if it were to simply absorb the neutron.

Homework Statement Consider a balloon filled with helium gas at room temperature (T = 294 K) and atmospheric pressure. Calculate (a) the average de Broglie wavelength of the helium atoms and (b) the average distance between atoms under these conditions. The average kinetic energy of an atom is...

Homework Statement can liquid helium at 4k (.1 nanometers interatomic spacing) be modeled by non spreading wave packets? Homework Equations 1/(√2π)∫∞-∞ei(kx-wt)Φ(k)dk W(k) was Taylor expanded to a quadratic term Δpx2/(2mħ) The book then sas for a non expanding wave packet: |t| << mħ/Δpx2...

Intuitively I always thought He was more expensive than Ar as a shielding gas. But I was reading this book about Heat Exchanger Design & it has this quote that claims "Argon is costlier than Helium" (Link below; see Bullet Point...

Hi all, Does anyone know where I can find data details of how Emission Spectra depends on temperature for the following materials: Single Hydrogen Molecular Hydrogen (H2) Helium That is, as I heat up each of the above materials by themselves, from room temperature to thousands of degrees, I'd...