Hot Definition and 560 Threads

Hey guys, I'm a bit confused about how hot/cold dark matter plays into our theory of structure formation. Hot Dark matter is relativistic then it decouples in the early universe, and these particles are light and fast and do not form small structures since there is a large mass needed to keep...

My title is a bit lacking, I know! So computers and electronics are typically creating waste heat and are ventilated out, sometimes not so efficiently. However, I was wondering if a computer or router or something actually generates extra heat simply because it is running hot, all other things...

Would it seem reasonable that so-called ‘hot jupiters’ are in resonance i.e. have a stable orbit? If one utilized our stellar system as a simulation, with the addition of a hot jupiter, then what would the resonance be? Would it be calculated as non integral? Then if our cold gas giant were...

I'm looking for information on how hot swap PSUs as used in computers (used typically for data center servers) are designed. In particular, I want to focus on the common aspects between the 2 or more PSU subunits that can be swapped. What kinds of connections are made between the individual...

hot water! (energy conversion) Hello colleagues I´m new here and I'm from delicias, Chihuahua, Mexico and the reason of my post is that I want to do something with the water that is discarded of the mine of Naica, Chihuahua because this water from the mine has a lot of energy, I mean the water...

This can be in any sort of science although research in mathematics and physics would interest me most as it would be consistent with my current majors. If you're wondering why I'm asking, it's because I want to maximize my chances. The more research has been done in a field, the harder it...

Do you frequently have hot debates with friends? Or cold debate maybe. (whats the difference?) I used to have such debates with my close friends which mostly went like this... A: No, you are wrong. Actualy its like this..... B: Ha Ha, you are a such a dumb. You forgot to realize this, ... A...

I actually would like to know two things... How hot is the fire from burning vegetable oil straight up? (like in a bowl) and How hot is vegetable oil fire when a bowl of oil is on fire and then water is poured onto it? (big fire) I googled but only found flash point info and how to...

I know there have been some forums here about hot air rising, but I'm curious - how fast does hot air rise? Also, how fast does it disperse? If we consider steam, for example, rising and dispersing horizontally from a boiling pot of water. Does anyone know some (hopefully simple) equations to...

We know that the particles in the hot universe obey Fermi/Bose statistics, but when we calculate the scalar dynamics i.e. in inflation or dark energy... and maybe also something else, it seems we don't take into account the statistics and just use one scalar field to calculate all these...

Homework Statement Hot water is mixed with an amount of ice having an equal mass to that of the water and an initial temperature of 0 °C. The specific heat capacity of water is 4.2 kJ/(kg K) and the specific latent heat of fusion for ice is 334 kJ/kg. Assume that no heat is lost to the...

OK guys Can anyone tell me some hot research problems in theoretical quantum optics/cavity QED right now ?

Homework Statement Estimate the average temperature of the air inside a hot air balloon. Assume that the total mass of the unfilled balloon and payload is 500kg. what is the mass of the air inside the balloon? No volume or radius is given, so I estimated V = 2800 m^3 & r = 8.75 m...

This paper shows an interesting new approach to a theory of geometry + matter. Impressive preliminary results: http://arxiv.org/abs/1101.6078 Induced standard model and unification ==quote Barrett's introduction== This article concerns the problem of constructing a quantum theory of...

Hello, Say I don't like to drink hot tea, in fact I don't like to drink anything hot. It is beyond my comprehension why anyone would want to drink something above 40C ;) I have cup of hot tea 100C and i want to know how long will it take to cool down to 40C. \frac{\Delta Q}{\Delta t} =...

Guys are really great huh? Yes, world would be boring without guys. so... yeah. :) I want to meet some decent guys! nice ones :) or bad ones but who are actually nice. uh... probably will regret this thread later. so, any other girls want to meet guys? uh... join me on my quest!

if you plunge a hot metal (like wire) into water, the water temperature obviously increases. I wonder what kind of heat transfer occurs between the metal and the water. it clearly doesn't seem like convection or radiation. But I am not so sure if conduction is the right one cos it is usually...

In which fields of science are there currently shortages of specialists? I'm looking for specific fields within physics, within engineering, or within any other sciences. Thanks.

haw can i calculate the thermal energy (watt or BTU ) of the hot air (or the exhaust air of the chimney) according to the following : Temp. : 250 C hot air flow rate : 11 000 m3/h thanks

Part of an experiment involved measuring the intensity of an X-ray beam through a piece of aluminium as a function of emission current of the X-ray source. I originally fitted a linear fit to my data (although it does start to level off at high emission currents). The marker however said that it...

Hello, I have the following question, I am trying to build a home made hot air gun for electronics soldering, my approach was with a modified Microwave oven transformer, multifilar 12mmxmm copper cables, and a 15cm stainless steel tube, the air is pumped from a powerful aquarium air pump. The...

Curious question, figured what better place to ask than the physics forum. So I just picked up a used hot tub. Was running great when I bought it. Filled it up with water, turned it on, started its cycle. It can take over 24 hours for the tub to reach 102 degrees. There's a 12 inch...

Hi. Often, when I am a tour guide at the Museum of Glass, Tacoma,WA. glassblowing shop. I get a question for which I don't have a definitive answer. I thought someone might know. The question is "why don't the glassblowing pipes(steel tubes, 4.5 feet long, .75" wide) get too hot to hold" Some...

This may seem like an odd forum for this question but I couldn't find an answer anywhere else. Why is it always recommended to rinse the dishwashing liquid and bleach with cold water, rather than hot, when cleaning a jacuzzi tub. Doesn't hot water dissolve and rinse better? My guess is energy...

Homework Statement 1 mole of Hydrogen gas at 300 Kevin is contained in a thin walled copper container. In container #2 there is 1 mole of Neon gas also at 300 Kevin. The volume= 22.4 liters and surface area ,A = .476 m^2 The surroundings are at 100 deg Kelvin. The specific heat of H2= 5...

Hello, I came to consider the following problem, and cannot seem to find the right way to tackle it. It is not homework, merely a question I'd like to address out of personal curiosity: Consider two volumes V1 and V2, each assumed adiabatic, and linked with a valve. V1 is considered...

Homework Statement Estimate the required temperature of the air inside a (rigid) balloon in order for it to achieve lift off. Volume 2000m3 \summass, mtot=920kg Homework Equations pV=NkT p=\frac{Force}{Area} \rho=\frac{m}{V} The Attempt at a Solution We require Fup>(mair+mtot)g (assume...

Must a "Hot Jupiter" be relatively young? A large proportion of exoplanets so far discovered are "hot Jupiters," large gas giants orbiting very close (< 0.1 AU) to their primaries. It seems to me that a gas giant orbiting at such a close distance ought to experience significant friction as...

Ive heard how radium can be radioactive and give off much heat but still be safe. But is it hot enough to ionize gas and make plasma? Can anyone help me?

Hi , what are the main astrophysical research topics these days , binary pulsars , black holes ? do you have any propositions ?? :)

If there is a hot air balloon and it flies into the air and stays there after 24 hours will the balloon have gone around the world once?

My physics problem is as following, Estimate the average temperature of the air inside a hot air balloon. Assume that the total mass of the unfilled balloon and payload is 500kg. what is the mass of the air inside the balloon? we are told to use a radius of 15m Equations needed density = m/V...

Homework Statement A hot air balloon is ascending straight up at a constant speed of 8.10 m/s. When the balloon is 13.0 m above the ground, a gun fires a pellet straight up from ground level with an initial speed of 28.0 m/s. Along the paths of the balloon and the pellet, there are two...

What are the hot areas in EE right now? By "hot", I mean the areas with the most job growth, the most prospect for development, the most needs and the most questions to be answered. (Analog devices? Digital design paradigms? Signal Processing? Meta-materials? Optical Networks...

Is it possible for heat to transfer from a colder atom (slower moving) to a hotter atom (faster moving) I know that hot and cold are not really appropriate words to be using here. My reasoning is from kittel thermal physics, From an entropy standpoint, The most probable...

Any literature on the big bang usually describes the initial moments as hot and dense. The laws of thermodynamics point to a universe where entropy is increasing, so given the assumption the universe is a thermodynamically isolated system, this implies a low entropy big bang. given that minimum...

I have got an electrical problem! Could you respectable electrician experts please give me some much needed advice? On eBay I bought a couple of these tankless, instant hot water heaters for use on 220VAC...

I have heard that warm water helps to open the pores of your skin, and therefore, can release more heat which will aid in the treatment of a sunburn. I was immediately skeptical, but after a few searches I found answers both for and against it. What are the actual physics behind this, and, if...

In hot air balloons the air inside the envelope stays at atmospheric pressure because of the hole in the bottom and the volume of the envelope is essentially constant. Yet in order to raise the balloon it must be heated which increases the its temperature. If the temperature increases how does...

Which sub-fields of EE are the most in demand right now? How about for the next 10 years or so? I'll be graduating soon and want to best position myself for the job market.

Hello, I want to do a test heating a hot dog in a tube using a Magnetron from a 900W Microwave oven. Before doing the test I would like to know if there is any reasons not to mount the magnetron antenna on top of the metal tube, or on the side. (Please see attached picture) Also, will I...

:devil: {Drum roll} It's so hot that it makes me want to take off my skin, and sit in my bones...

Homework Statement I have been working on a University Physics thermodynamics problem for over a week now, day and night. I've consulted two physics PhDs, posted on Yahoo Answers (nobody took the bait) and I'm still stuck. I just wasted an hour and a half carefully posting my problem and...

Hi all, I am wondering that we should choose fast or slow function of electric Fan in hot weather, which function will spend much more of energy?, can someone give me an explanation :D Forgive me if the questions is silly

Ok i get that hotter air is less dense , but when light goes from hot air to colder air we are dealing with the same atoms it is just that the photon will have less collisions , why would the angle of re-emission change for the photon just because it is having less or more collisions in the...

Homework Statement To reduce heat loss, the surface area of a hot-water tank must be kept to a minimum. If such a tank is 125 litters in capacity, and can be approximated by a cylinder in shape with a hemispherical end cap; calculate the radius and overall height for minimum heat loss.hi can...

I put a AAA alkaline battery in my pocket and later detected warmth. I took the battery out of my pocket and it was very hot. The only other items that I had in my pocket were a few coins and a key ring with keys and one of these plastic security fobs. I can only presume that some kind of...

I'm a high school science student/aficionado (since it's sort of hard to specialize in anything in high school) and I have some relatively elementary questions: I learned in chemistry class that temperature is the average kinetic energy of the particles in any given sample of gas, so...

Homework Statement A hot air balloon has a volume of 2000m^3, and air is always at atmospheric pressure due to large opening. What is the mass of the air if the temp is 120*c. Assume a molecular weight of 28.8g/mol for the air) Homework Equations PV=nrt The Attempt at a Solution...

Hi everyone Today, me and my brother made pancakes for breakfast... after we finished to eat I started to clean up the skillet... to made the cleaning action easier I filled the skillet with hot water (which were white), then I left the kitchen for few minutes. When I came back I found out that...