Hot Definition and 572 Threads

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A typical UK domestic hot water tank holds c. 200 litres of water. Hitherto the common method of heating it to say 60C has been by means of an internal coil of copper pipe through which is pumped hot water from a gas boiler at ~ 70C. Heat transfer on the outside of the coil is by natural...

Is it possible to estimate the number of hot and cold spots of average diameter of 1° in a full-sky map of the CMB?

I have been reading about the Ranke-Hilsch vortex tube. Details of the explanation tend to differ somewhat among different sources, but it got me thinking about the following thought experiment. Air enters a tube of about 0.5 x 4 cm cross section. It passes through a section that is channelized...

https://phys.org/news/2023-01-astronomers-super-hot-stars.html https://academic.oup.com/mnras/article/519/2/2321/6967306?login=false

Im a keen camper and for my family tent I have been a long time convert to airbeam tents as opposed to poled tents. There is a lot of anecdotal evidence that the recent spate of hot weather has led to increase in burst airbeams due to the higher temperatures, but i find it hard to believe that...

https://www.physicsforums.com/threads/how-hot-is-it-2021.1004617/ Now 13 months later. This week is supposed to be the hottest of the year, at least for us locally. The last two days, our backyard thermometer reached about 102.5°F (39.2°C) compared to the local weather station with an...

Manufacturer information: Interior material: stainless steel Exterior materials: Stainless steel Keeps cold liquid for: 24 hours Keeps hot liquid for: 12 hI was looking for a thermos bottle and came across a situation that I'm having a hard time answering. Why is the cold keeping time different...

The idea will be presented at the ancient Venus conference https://www.hou.usra.edu/meetings/ancientvenus2022/pdf/ancientvenus2022_program.htm Houston 25 Jul. The abstract: https://www.hou.usra.edu/meetings/ancientvenus2022/pdf/2024.pdf Some of the earliest members may remember a thread about...

I was studying wind formation from the continent to the sea during day (direct circulation) and the explanation I found in almost all the textbooks was that: 1. In the continent during day the ground becomes hotter 2. The particles in the air increases their temperatures due to induction 3. When...

Hypothetically how can someone build a small hot air balloon? I want to navigate a 360 camera to the air without needing a drone. Just a balloon, camera, and string to keep it from getting away. Maybe a remote fan to pull it down if string gets loose.

Hi guys, M can then be split up into 2 components: the mass of the payload which is known, and the mass of the wing. The wing material has a known thickness and density meaning its mass is given by: surface area of wing* mass per m^2 (mass m^2 is used as density and thickness are known so an...

Hi, The solution for this question is thermal energy lost= thermal energy gained 0.200x450x(300-T)=1.0x4200x(T-20) T=26 degrees celcius. However, I am struggling to grasp why (300-T) is used. I have always known a change in something to be final - initial. Therefore change in T= Final-...

I'm reading about the engineering of the James Webb and it surprised me that the temperature difference will be about 318 degrees from one side of the telescope compared to the other (85 C on one side and -233 on the other). I didn't expect space to be that hot about a million miles further...

Sorry if the question is dumb. Please be kind to help

Hi In some projects, I saw that hot and cold water tanks have been used for open circuit cooling towers. What is the need to use these tanks?

I have computed ##T_x## and ##T_y## and evaluated it at the point (20, 20). ## \frac {-450*x}{x^2 + y^2 + 1)^(\frac {3} {2}} - \frac {420*(x + 10)} {(x + 10)^2 + (y - 20)^2 + 1)^(\frac {3} {2}}, \frac {-450*y}{x^2 + y^2 + 1)^(\frac {3} {2}} - \frac {420*(y - 20)} {(x + 10)^2 + (y - 20)^2 +...

Now a high pressure heat dome is sitting over eastern Washington, Oregon and northern Idaho, and up into Canada. Cities and towns are experiencing record temperatures for June. Normally such temperatures aren't experienced until mid-to-late July or early August, if at all. AP - Seattle hit...

I like cup noodles that come with convenient packets of seasoning or sauce. From time to time I forget to take away all packets before pouring hot boiling water into it. In most cases those packets are printed with color and are made of kind of plastic or tin or something with metallic color, I...

Volume of hot air ballon V=((4/3 pi R^3)/2) + (1/3 pi h (R^2 + r^2 + Rh) = 2956.24 m3 Balloon: R=9m h=15m r=1m m = 750 kg H = 5000m T = 373 K p1 = 101300 Pa p2 = 50650 Pa M(air) = 0.029 kg/mol F = mg - 7350 N

I have solved the first 2 parts. For the 3rd part, I have obtained the equation: T(x) - T0 = (T1 - T0)e^(-Φx/fc), where f = fm in the question. How do I obtain that expression for H? Thank you!

Hello This is not a homework, this is my own experiment to understand how the motion works. Please, follow my question here below: I have a hot wheels race with a slope with 10 degrees where I use a small car which departs from the top to the bottom. I have taken 5 times the time to get an...

I don't normally wash clothes with very hot water but in order to eliminate clothes bugs I need to soak them in very hot water, as advised. I'd like to know what kind of clothes or texture should avoid being soaked in very hot or boiling water? The only texture I can think of is artificial...

So I've been hunting google for an answer but i cannot find a definitive one. If 0 Kelvin is the coldest temperature and it is where atoms cease to move does this mean that a photon in a vacuum is the hottest particle because it is in turn moving at the fastest speed possible? Second question...

I mention the details in the book (verbatim) in the form of a paragraph in green below. Later I ask my questions in blue font for better reading. "Surface tension also explains why hot, soapy water is used for washing. To wash clothing thoroughly, water must be forced through the tiny spaces...

Condensed, simplified version:: https://www.livescience.com/physicists-entangle-15-trillion-hot-atoms.html The link at the end of the article does not always work, here is one that does. The research article: https://www.nature.com/articles/s41467-020-15899-1 Cheers, Tom

Summary:: The Hot chocolate effect is an investigation that extracts the essence about the effects on speed of sound. This is carried out in this sequence: A cup filled with liquid is continiously being tapped from the bottom. Meanwhile, a disturbance in the longitudinal sound waves is being...

First, I tried using the Archimedes principle and calculated the weight of the surrounding air displaced when taking off. ##W = 2500\times 1.29\times 9.81 = 31637.25 N## But then, I got stuck and do not know how to proceed from here on. I don't want the full solution yet but can I get some...

I have two more questions:- (1) Can we calculate the time it takes specifically for water to radiate all its heat? (2) Heat is illustrated as kinetic energy of molecules, so why collision between particles should result in the conversion of kinetic energy into radiation. Why conservation of...

<mentor - moved to Engineering> Hi, I would like to know how the glucose content can be measuring in hot beverages using non-intrusive method. Thankyou

This is a past exam paper Q. I think i might be missing info though. For i) i use q=UAdT A= 35m2 dT= (80-20) They haven't given U but if i know answer should be 1,050W So if i set U to 0.5 (0.5)(35)(60) = 1050W Am i missing something or could I calculate U with the info given? Also ii) Use...

I know typically the hot cathode of an electron gun or vacuum tube is heated either directly or indirectly by electric resistance heating. What if the tungsten (cathode) were heated by another means, say focused sunlight? Electrons would still boil off through thermionic emission. If a small...

I have two coffee mugs (I have many more, just not in this example :biggrin: ). I often microwave cold coffee from earlier in the day. Mug "A" when microwaved for a minute produces hot coffee and a warm outer mug. Mug "B" produces hot coffee and a lava hot outer mug that will give you third...

Just a question that's been bugging ,me, In the first seconds of the universe it is stated that a hot plasma was the seed of the universe, can some one please tell me how the plasma got hot in the fist instance. thanks.

Hi, I was just wondering about the efficiency of a cycle that is not Carnot cycle. In that case one should use \eta = 1-\left|\frac{Q_{\rm out}}{Q_{\rm in}}\right|, where Q_{\rm in} and Q_{\rm out} are the amounts of heat absorbed and released during the cycle. For instance, I guess that in...

I have read about many hot box apparatus made by guarded hot box method. My question is why do people do not make one where the hot side consists of a heated metal plate directly in contact with the material to be tested. For those who do not know about what a hot box apparatus is - It is a box...

Hi, If it is assumed the temperature of a shower is to be 43°C and the electric shower consumes 50 litres of water at that temperature, then the Energy required for an electric shower would be: QElectric Shower = mcΔT QElectric Shower = 50 * 4.181 * (43-10) QElectric Shower = 6.89945 kJ or...

As I understand it the fact the COBE measured the CMB to be a perfect black body implies strong evidence for the hot big bang. However, I am wondering what was the earliest prediction that this must be so from big bang cosmology? Does it go all the way back to Gamov and Alpher? is it older ...

What is the origin of the fact that heat flows from hot to cold? Does it have something to do with fluctuations?

It was hot and I bought a tub of ice cream to take home. I put the AC on and blew into the footwell where the ice cream was. Was that sensible? Is it better to let a static layer of cold air surround the tub of ice cream (say at -5C), or to blow cold (~+10C) air over it when the ambient in...

Trying to understand the concept of heat. As I understand it, heat is really just kinetic energy. In Newtonian mechanics, it is 1/2mv^2. Here are my questions... (1) On a microscopic level, are conduction and convection simply atoms bumping into each other and passing along some of their...

Question in the title .

This probably occurs with salt too but let's concentrate on xylitol: you heat water till it boils, put the hot water in a cup and add a tsp of xylitol. It boils again violently for a couple of seconds. The high school explanation is that the boiling point of the water is lowered. I'd like to...

Initially the hot air balloon is stationary so... FB=Fg ρgV=mg m=1319.2...kg FB=Fg=12941N In the air... a=2d/t^2=0.933...m/s^2 Fnet=FB-Fg (1319-x)(0.93...)=12941-(1319-x)g x=114.6 kg but apparently this is wrong?...

If one hooks up solar panel to bottom element after removing AC line seemed like good idea then I was wondering if the wires going to the element will get hot instead of the element see drawing.

30% of the students who came into a coffee shop talk to Dan's for his office hours. 20% of them got hot chocolate. 50% of them got nothing. Only 20% of the people in the shop during those two hours were students coming for Dan's office hours. Out of this larger group, 65% got coffee, 10% got hot...

in Clausius formulation, what does the phrase "from cold to hot" means? I can understand it intuitively but in the language of the zero and first laws, we have not defined a temperature scale, only equivalence classes of systems that will be in equilibrium with each other (systems with the same...

I tried following: $$ dS_{\text{total}} = |\frac{dQ}{T_c}| |\frac{dQ}{T_H}| $$ where ## T_h ## is temperature of hot water and ## T_c ## is temperature of cold water. Coefficient for water wasn't provided in the assignment so i used following value c = 4190 J/kgK. $$ dS_{\text{total}} =...

Authors revisited the famous Gilovich, Vallone, and Tversky paper from 1985 that 'disproved' the existence of a 'hot hand' or serial correlation in shooting attempts and found a subtle sampling issue, that when corrected for, actually proves that hot hands exist...

Will a hot water heater element that is rated 220 volt AC by 2000 watts when only applying 110 volt AC just put out 1000 watt instead?