Formation Definition and 480 Threads

Hi, I am trying to understand the formation of Copper pairs in a superconductor. However, 2 major explanations I found in the internet: 1, Cooper pairs are formed by emitting and receiving phonons between 2 electrons. 2, another explanation is, when an electron drifting between the...

Discussions involving Hawking radiation in the study of black holes usually require their preexistence; however, if we apply the Hawking radiation process to the initial stages of a birthing black hole I'm confused about how the theory claims the event horizon would form in the first place. In...

When you look in spoon from a reasonable distance you see an inverted image of yourself in the mirror. How can you see a real image in the mirror when I thought you saw virtual images in a mirror and real images had to be caught on a screen.

Is it feasible to form a S+ cation? Goin on the basis that the electronic configuration is 1s2,2s2,2p6,3s2,3p4 the valence electrons would be 3s2 and 3p4. So I'm thinking that it would be relatively easy to remove the 4th electron in the p subshell BUT looking at the 6 valence...

I have a thought whilst in the shower this morning, it is usually said that shock waves only take part in star formation when other stars have formed and have exploded as supernova sending out a shock wave. Now I have been thinking, the usual equation for self gravitation is given by...

Dear friend: i'm a fresh man, some concepts puzzle me. As the title says, can anybody tell me what's the different between the binding energy and formation energy? Regards

please can anyone explain me in simple words why energy is released when bonds are formed?

I know that in the process of fusion in Stars, the hydrogen fuses into helium and so on until Iron is formed. The fusion stops after the formation of Iron and the graviatational force wins to take over the star evolution. Then how do we account for the elements which are havier than Iron?

Homework Statement The standard heat of formation of n butane cannot be measured directly but can be determined indirectly from other heats of reaction by applying hess's law. Given the folowing data for the combustion of carbon hydrogen and n butane in oxygen: C + O2---> CO2 H=-393.5...

Homework Statement Formation of the Solar System The distance of Venus is about 0.7 AU, and the orbital radius of Jupiter is about 5.2 AUs. How many times hotter is the region where Venus formed compared to the region where Jupiter formed? Enter numbers and decimal point only. Round off...

Suppose traffic is moving uniformly with a constant density $\rho_0$ when a traffic light turns red. At time $t = 0^+$, the initial density profile is then modeled according to the figure below. The resulting wave motion of the disturbance is governed by $$ \frac{\partial\rho}{\partial t} +...

Homework Statement We already know that standard heat or enthalpy of formation of a substance is the heat change in forming one mole of the compound from its element in their standard states. Thus in the reaction the enthalpy of formation 2 mole of NH3 is 92kJ. Therefore the standard DH of...

I liked this graphical example of black hole formation posted by PAllen in another thread and I want to discuss it. It is not unusual that arguments defending existence of black hole go like that: 1. Assume that BH exists. 2. Then observer falling into BH ... I think that point 1. is...

Could it be possible that our universe was created when another universe bumped into ours thus creating a chain reaction and perhapse sharing its matter with ours? I have this idea the there are billions, trillions or any number of universes in a empty space sort of like how galaxies are mostly...

I came across a question about wave from univeristy physics (sears n zemansky) and the question was 'can a standing wave.be produced on a string by by superposing two waves traveling in opposite direction with same frequency but different amplitudes? And same amplitude but different...

Hi. I am reading about the pn junction, but I have a question. When the junction is formed the holes in the p-type material close to the junction diffuse across due to the concentration gradient. This leaves the acceptor atoms in the p-type material negatively charged. My question is: when...

How does one analytically estimate star formation rate in a plasma cloud? Could someone lead me to original references? Kennicutt-Schmidt Law, I guess, is empirical.

How does one analytically estimate star formation rate in a plasma cloud? Could someone lead me to original references?

Hi, In the case of the gravitational collapse of a star where neither electron or neutron degeneracy pressure is sufficient to prevent further collapse, is there a possibility that the star will become a quark star rather than a black hole? From what I understand, quarks are perpetually...

how is the rapid escape of air from a burst tyre and cloud formation in atmosphere an example of adiabatic process? please explain

Homework Statement Well,actually it isn't related to my hw.I ask this just simply due to my curiosity. Here's the question: Sometimes,we saw bubbles formed on the water surface,could anyone explain this phenomenon:)?Any theorey behind it? thx a lot. Homework Equations The...

Confused about the formation of "Stuff" in an Isotropic-ish Universe First let me state my current understanding so that I can be corrected if not on the right page-- Given "zooming out" far enough, our universe is rather homogenous/isotropic, but not perfectly so. If this is correct, I must...

How are Pions produced inside a nucleus? I've heard it was through gluons exchange but found nothing about it.

How can be the black holes formed in proton -proton collision

I hope this isn't deemed school related. It is something I learned in school, but I'm now trying to figure out a reaction model for my work. In the process of calculating the reaction constant, usually you first determine the Gibbs energy of formation of each species, find the difference...

Homework Statement In my book it is given that ΔHffor NaCl is less negative than that for KCl. I'm not able to understand that...I think that electrostatic attractions between Na+ and Cl- will be stronger than K+ & Cl- as Na has smaller size than K...in its formation more energy should be...

Hi All, I've done a quick google, and I can't find anything obvious (first 3 pages) about the formation of magnetic fields, specifically, how does the distribution of magnetic field through space take place as an electrical coil is switched on? As a secondary question, is it possible to...

What does metallicity have to do with stellar formation? Why does low metallicity in stars in the very early universe mean that they needed to be more massive than modern stars to form?

I have no problem with description of a small star's formation by gas and dust accretion. The problem I have is with a massive star. When enough material has accumulated to start the fusion of the star, a stellar wind will start and will clear away the gas and dust nearby. A heavier star would...

H3+ The original mothercloud was mostly H2 and He. It didn't have molecular species containing C, N, and O that are good at radiating away heat they pick up by jostling each other when the cloud contracts. So it was hard for the early clouds to contract by their own gravity, because they...

can anyone tell me how the orifice diameter can affect the vortex forming ? no much info from internet , thanks for help~:smile:

Homework Statement An object 2.00cm high is placed 12.0cm in front of a convex mirror with radius of curvature of 8.00cm. Homework Equations Where is the image formed? Draw a ray diagram The Attempt at a Solution do i use the equation m=-q/p? if so then (object distance)p= 12cm...

Hi I have a few questions regarding gas dynamics... 1. when M=1, dA=0...what does this mean? Does it imply that if we have a converging (subsonic) nozzle with its exit mach no,say 0.8, and then direct the flow to a constant area tube, then we have to attain M=1? 2. When we know the length...

Background: I've seen many different values for enthalpy of formation on Wikipedia, such as the following: MgO: -602 kJ·mol−1, Fe2O3: -826 kJ·mol−1, NO: 90.29 kJ·mol−1. I'm curious about these values, but I have no idea how they were determined and I've only taken an introductory course in...

In another topic, a member dave13214321323 or whatever his name is :p said that the popular opinion is that in the early universe gas contracted into denser spaces forming galaxies and black holes were consequences of galaxy formation, not the other way around; Black holes at centers of galaxies...

How to avoid formation of Lithium Chromate ? I am willing to make a glass batch which consists of Li2O and Cr2O3 as well as other stuff... My concern is Lithium Chromate which shouldn't form due its undesirable color. How can I possibly avoid formation of Lithium Chromate at about 1000C ...

Hello everyone, I've been trying to figure out why when ionic compounds are formed that they are exothermic (meaning they give off heat). The only theory I have is that when the ions are coming together, the motion from them moving and possibly the friction of their surfaces making contact...

I am reading on wikipedia about internal energy and the describe it as the energy required to create a system. Ithought that this was the definiton for enthalpy of formation. Was it meant by the definition of internal energy?

Hey, I've looked for a little bit just online and in the forums and still have not gotten a definite answer. My question: why does bond formation release energy? There is a reason I am posting this is the Quantum Physics section. I am very certain that the energy released into the environment is...

In Acid Rain caused by car emissions, how does NO2 and OH from water chemically bond to form HNO3 (Nitric Acid)? From the subatomic and a skeletal formula perspectives, please. Does one covalent bond overpower another? How does the formula rearrange itself step by step?

When we see an arc between a Jacobs ladder is this because a charge density builds up between the rods and then the E field between the rods is strong enough to rip electrons off the molecules in the air and the start to conduct.

How the depletion region act as capacitor? My view is that there are no charges because if formed of recombination of charges. so, there is no charge... So, how can it act like a capacitor? How the electric field is created in depletion region? It's confusing me a lot ...

Homework Statement Create cis-1,2-epoxy-1-phenylhexane from (E)-1-phenyl-1-hexene Homework Equations The Attempt at a Solution My teacher asked for two ways to create this and I think I've got the first. The first way was by treating (E)-1-phenyl-1-hexene with H2 and poisoned...

For my advanced physics lab course this semester, I recently conducted an experiment using a hyper-pure germanium detector to measure the energy of gamma rays released upon the formation of deuterium (DF). Essentially, I used a neutron source to bombard a hydrogen rich target (used both...

I have been having trouble with this for a long time 1st - How and Why is a image formed ? 2nd - If all objects reflect light why is the image not seen on all the objects Even walls reflect light but there is no image formation when light rays from an object reflect off an object and...

The understanding of the origins of our planet (as well as the other planets in the Universe) has always remained a question to astronomers. Inherently, the application of Newton’s known concepts of gravity has granted us the ability to make educated assumptions concerning planetary formation...

Hi all, I recently encountered this scenario. I placed a (1 litre) glass bottle with water (about half filled) that is corked up near my stove. My wife was cooking and the cork suddenly popped. We discussed this over dinner and I said that it was due the air in the bottle that has...

Hi guys So I went on a field trip with my class and this is one of the things we saw: http://74.52.147.194/~devilthe/uploads/1320293567.jpg Can anyone tell me what that is from? I think maybe it's from a glacier or something of that sort that caused it...but I really have no idea and...

A concave lens always forms a virtual image (for a real object), will it always form a real image for a virtual object? (that is, when rays converge on it) If yes, why? If no, why?

When a massive star dies, you either get a neutron star, or a black hole. From my lecture, neutron star are extremely hot object, with temperature around 10E11 to 10E12 kelvin. I'd assume black hole created from a similar process with just more mass, wouldn't have temperature any lower...