studiot

Well there several forms of energy, but energy there are also other quantities / properties that can be considered. However you have to start somewhere and energy is a good starting point because most people have a reasonable intuitive feel for it, that just needs sharpening up to scientific standard. Energy is a property possessed by material things (matter) and some non materieal things (sunlight, radio waves..). There are several forms of energy and there is a fundamental law (the law of conservation of energy) which states Energy is neither created nor destroyed, it is merely transferred from one object to another and/or changed from one form to another, in some process/interaction of interest. At this stage is is not wise to be diverted by subjects like zero point energy, many worlds, quantum chromodynamics (and many others) which are extensions of the basic idea. In physics we like to consider one process at a time and when we do the energy change(s) associated with that process may occur over a whole continuous range of values. (for example any value between 1 and 10 units, including fractional ones) Changes of this sort are considered by what is called classical physics. Alternatively the energy changes may only occur in certain specified values (eg 5 units and 10 units exactly and only) Changes of this sort are considered by quantum physics, the discretisation of a continuous range of available values into only a few specific values is the main idea behind quantum physics. To return to my original question, we can easily explore the above in relation to two forms of energy - viz kinetic energy and potential energy - once you know what these are. So please tell me what you think they are if you wish to continue.

This site has a good picture and short explanation showing the workings of the eelctrochemistry of the Daniel cell and the salt bridge that Nicholas mentioned. It also explains why the two halfs of the cell are kept separate, can you spot this? http://chemwiki.ucdavis.edu/Analytical_Chemistry/Electrochemistry/Voltaic_Cells/Case_Study%3A_Battery_Types/Batteries%3A_Electricity_though_chemical_reactions This site is generally useful about modern theory and applictions of batteries. http://batteryuniversity.com/learn/

Well since you didn't pay much attention to quantum theory in school. did you pay any attention to the basic stuff that comes before it? Without an appreciation of this quantum theory is indistinguishable from magic. Do you have at least a feel for what energy is and what shapes and forms it comes in, because quantum theory is largely about energy.

Yeah, series are very important. Look in you university library for the book Infinite Series by Fort Oxford University Press

That is a very good point unity+. (+1) This is where I was trying to lead. For Prose you may have seen some expositions of convergenge but have you seen this one? First the idea is that the controlling definition is convergence. If a sequence or series is not convergent it is divergent.. So the tests are basically (nearly) all for convergence. Now a definition of convergence is meant to convey the idea that, after some the Nth term in any sequence every term is within a certain distance of the limit. so for any term m > N : (TL - Tm ) <= some delta, however small. Or to put it another way a sequence is convergent if for any delta > 0 There is a TN such that every Tm where m>N is less than delta. Using this definition I would say that Unity+ is correct. Equally, by definition any sequence that does not satisfy this is divergent. So for instance if I had alternated +1, -1, +1. -1 etc then the above condition would not be met. Does this help ?

Talos, do you just wish to preach or are you interested in discussion, which involves acknowledging the contributions of others present in the discussion?

Extracted from your link. Yes that's exactly what I was trying to steer you towards. There is not one factor involved but a combination of them. The number of hydrogen atoms The number of lone pairs The geometry which is the result of hybridisation and allows attractions between lone pairs and the Hd+ all play their part. Note that the 4 and 2 are the max numbers of hydrogen bonds, not all may be established. Keep asking searching questions and you will go far. +1 for a good question

Well, Talos, you finally did post a link. This one is marginally better than the website under reconstruction you referred to before in that there is one statement I can agree with. Further the author seems to be under some misapprehension about vorticity in fluid dynamics. The air in front of the aircraft has zero vorticity, in general. Therefore, by Kelvin's theorem, the air some distance to the rear of the flying craft must also have zero vorticity. The trick is to create not one but two opposing vortices that cancel each other out over the region around and immediately behind the plane. For a craft flying from right to left across the page the surrounding vortex is clockwise and gives rise to the circulation in Jukowski's theorem and the downwash you have already described. The counter vortex is found some way behind the craft in the trailing wake. It is usually in the form of shed vortices from the wing tips. Concentrating solely upon the vortex surrounding the craft does not conform to Kelvins theorem.

In this case it is particularly important since the square is not parallel to the x and y axes.

H2O H1F How many hydrogen bonds (involving hydrogen) can each molecule engage in? I think the answer is 4 for water and 2 for hydrogen flouride Note also that boiling point increases with increasing molecular weight, in the absence of molecular interactions. Water is (16 + 2) = 18 : BP = 100C Hydrogen Flouride is (19 + 1) = 20 : BP = 20C Ammonia is (14 + 3) = 17 : BP = -33C Methane is (12 + 4) = 16 : BP = -182C So water and hydrogen flouride are anomalous, going across the periodic table, as are hydrogen sulphide and hydrogen chloride in the next line, for the same reasons.

Look here http://www.precisionmicrodrives.com/application-notes-technical-guides/application-bulletins/ab-004-understanding-erm-characteristics-for-vibration-applications

So how many hydrogen bonds must be 'broken' to release a molecule from the liquid to the gas in each case?

What are the shapes of the molecules and which ones have lone pairs?

So have you drawn a diagram from the information given?

If that was an answer to my post I am obviously wasting my time trying to help.

Pity you didn't answer my courteous reply to your post. I would have thought the answer to your question here fairly obvious, but often forgotten. Fuel is expended and work done to fill the balloon or drive the aeroplane.

This thread provides an excellent opportunity to clear up some misunderstandings of basic terms such as a field. An electron has no 'charge field'. This thread is about Physics so we neeed the physics definition of a field. In Physics, a field is a region of space where we can assign a finite value of some variable of interest to every point. Note this value must be finite, although it may be zero, and available at every point. Further we require that the change of values of this quantity from one point to the enxt is smooth or continuous. Some physical agent is required to create a discontinuity in a field. Think of a river. Every point in the flowing water has a water density, and every small parcel of water around that point has a mass. This (mass) would be analagous to a charge field if the charge were smeared out over the whole region of space. But charge is not smeared out, it is concentrated in particles (electrons in this case). We could address this by have largely zero values in our field, but we would still be left with discontinuities as we regard electrons as point particles at this level of analysis. So instead of talking about a charge field' we talsk about a charge distribution when we have more than one charge to discuss. If you are happy with this and want me to explain how this applies to a capacitor, I will be happy to do so. No it only conducts the electrons that have sufficient energy. In doing so they lose energy to the dielectric which in this case causes the dielectric to emit light. We know this because the light comes from atoms dropping down an energy level with the release of energy. Actually there's a good question will a van de graff generator in a vacuum still emit light? Though you can tell me what corona discharge is. Strange correctly understood what I was saying. The underlined part is true of all conductors, That is where the conduction electrons come from. These electrons only move when the applied voltage (did you forget that?) is large enough. That is where the energy comes from. Of course enough voltage to create the spark will have to be applied (I have already said that before) and , by definition all these electrons will have enough energy. You can reduce this by thermionic emission of course, (and study your question about light emission in a vacuum to boot). BUT The region between the conductors then becomes a conductor with measurable conductance (resistance) which, by definition, is no longer a dielectric. Dielectrics, by definition, do not conduct electricity.

Post#54 in this thread showed a lovely picture of the downwash, as already noted. I think it would be entirely appropriate to provide a proper link to the website you mention, as it is not advertising. As regards this thread, you have not answered my question, Where does the descending air come from?

Yes, but it may help to think about the question "Where does the descending air come from ?"

1) Have you never heard of relative velocity? 2) We are talking about 'heavier than air' craft which, unlike a helium balloon do not benefit from positive bouyancy forces. Why is it so difficult for people to accept that no laws are broken and that more than one physical law is in action in developing the lift force? There is a fluid, so whether it is standing or moving in a laminar manner you will always be able to apply Bernoulli's theorem to it. Whether or not this theorem supplies the desired result is another matter. Equally Newton's laws apply to this motion, or lack of it, since this motion is non relativistic. In structural engineering it is commonly realised that one may calculate directly witht he stresses and strains or convet these to forces and displacements or use energy methods, including the calculus of variations, or even some combination of these. Sometimes one method is easier than another, but all yield basically the same results. That is because they are all satified - they all apply. There are fewer options in aeronautical engineering so why is the same realisation so difficult? Both are extensions of the same continuum mechanics.

You should study sequences before you study series; they are simpler and it doesn't take long, have you done this? Your understanding of what convergence is, is also key. Can you say if the following sequence is convergent or divergent? 1,1,1,1,1,1,1,1..........................................1,1,1,..................1,1,1,.......

When the spark current is flowing the arrangement is no longer a capacitor. It is actually doubtful if the arrangement can be considered a capacitor even before the points are brought close enough to generate a spark. This is because the capacitance is proportional to the cross section area and you have shown tapering points, which in the limit tend to zero area, and therefore zero capacitance.

I am getting bored with this constant repetition of your false statement that there is charge between the plates of a capacitor. Since this is contrary to conventional thinking, please prove your words.

You have all correct answers, so what is the question?

I don't believe I mentioned the phrase 'charge field'. Where did that come from, and what do you think it means? There is no energy associated with the field generated by a single charge. Try reading this bit again. I have no idea what you mean by 'a separate field' either.