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1

Yes you are right. You end up having a varying electric field which generates a varying magnetic field which in turn generates an electric field etc... This causes a particular type of radiation called black body radiation.


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A cooler that has ice and water in it will be held at 32 degrees Fahrenheit until all the ice is melted. The rate at which the ice melts depends on the rate at which heat can enter the container. The rate at which heat crosses any thermal boundary can be modeled as: $$\dot Q=\frac{\Delta T}{\sum 1/h_i}$$ Where $h_i$ represent the thermal conductivity of ...


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Yes it is possible to have water coming out be colder than the water going in. Imagine a big pipe connecting a big container of ice water to a big container of boiling water. Then one end starts out colder than the other. Now raise the container of boiling water higher up so that water starts to flow from the boiling water to the freezing water. Heat ...


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The frequency of the first harmonic oscillation is the higher the higher the tension in the string. As temperature increases, the length of the string slightly increases. The change of linear mass density is thus negligible, but the corresponding change of tension in the string is not. The tension decreases and thus the speed of waves and frequency of ...


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Assuming you fix the temperature at the cell boundary, you can solve for the steady state temperature profile within the cell using (see any elementary heat transfer book) $$\nabla^2 T = -\frac{\dot q}{k}$$ where $k$ is the thermal conductivity on the inside of the cell and $\dot q$ is the heat generation rate per unit volume. The temperature only varies ...


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Resistance changes with temperature The temperature coefficient of resistance, or TCR, is one of the main used parameters to characterize a resistor. The TCR defines the change in resistance as a function of the ambient temperature. The common way to express the TCR is in ppm/°C, which stands for parts per million per centigrade degree. The temperature ...


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The thermal conductivity for water is k=0.56 W/m⋅K,all right,but this is for a lake,for exemple,when the heat transfer is between the air and the cold-water layer.The unit of measurement is W/mK ,not W/(m^2)K. So it's for the thickness ,not for the surface! If you want to calculate the heat production in the time unit ,H,start from: H=4π(r^2)ΔT α ,where ...


2

You've got your work cut out for you, so this answer can only point you in a direction. This calculation can be difficult because there is a profusion of pieces of terminology with subtly different meanings. Find a book/other source (but for the straight dope I suggest a book) which discusses radiometry and the differences between radiant flux, radiance, ...


1

Moving water doesn't freeze as fast as still water. Boaters who leave their boats docked in bodies of water that freeze over install bubblers at the dock to keep the water moving. The effect is that the immediate area around their boat doesn't freeze over. It's the same principle for running water through you faucet to prevent a freeze. That is part one ...


2

Note that to figure out how quickly an object heats up, you need the ratio of two quantities - the thermal conductivity, and the volumetric heat capacity. If the former is large AND the latter is small, you get an object that will quickly take up the heat of its surroundings. This parameter is known as the "thermal diffusivity" $$\alpha = \frac{k}{\rho ...


3

Yes this does really help. Due to the density anomaly of water it expands even when it's frozen and in a solid state (ice). This causes your pipes to burst over the time due to the increased pressure. Letting the water dripping a little bit serves as a pressure relief and therefore prevents the pipes from bursting. It is important to run both, hot and cold ...


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To a good approximation the radiation emitted from a hot piece of steel will be the same as emitted by a black body. The relationship between the wavelength $\lambda$ of light emitted by a black body and the temperature $T$ is given by Planck's law: $$ B = \frac{2hc^2}{\lambda^5} \frac{1}{e^{hc/\lambda k_b T} - 1} $$ where $B$ is the spectral radiance, $h$ ...


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Practically speaking, diamond has the highest thermal conductivity of any "reasonable" material, about 5 times greater than copper. Additionally, its specific heat is about 30% greater than copper or brass, but about 10% that of water. As a result, a diamond will heat up faster than just about anything else, particularly when immersed in a liquid like water ...


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An object at 1000K glows red because that is basically dominating the radiation that it is emitting that we can see. Most of the radiation it emits emerges in the infrared part of the spectrum to which our eyes are not sensitive. Your edited question asks about the appearance of hot metals. The chart below is an example of a "colour-temperature" chart for ...


4

Are spectra (both fluorescence and absorbance) of any molecule dependent on temperature? The characteristic wavelengths do not change with temperature but the intensities will. As temperature changes, the relative concentrations of molecules with particular energy levels will change and that will affect the relative strength of absorption bands and the ...


1

I am unsure of the solution below because of my free manipulation of P and Q, so if anyone has a comment or better way, let me know. Some assumptions: I assume that in the question you meant that we have a body with a surface area $A$, which is at an initial temperature $T_{0}$ and is losing energy by means of radiation, for which you used the ...


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If the room is isolated (can't exchange heat with the rest of the universe) then the air conditioner must be "part of the room" and only able to draw in air from the room and expel air to the room. Also, the power source for the air conditioner and fan must be inside the room, otherwise the system isn't isolated. So let's say we have a battery to operate ...


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There's no question that the quickest way to cool all the air in the room is by using the fan to circulate hot air into the air conditioner. But in a thermodynamically isolated room, the air conditioner dumps hot air, as well as cold air, into the room. It's unwise and energy inefficient to use an air conditioner in a truly isolated room. You need to ...


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If you measure that it takes an apple 2 days to rot, then you note that another apple (which happens to be colder) takes 3 days to rot, you could either conclude that time has slowed down, or that the rotting of an apple does not make a very reliable clock. I conclude the latter. A cold apple and a hot apple are both experiencing the same passage of ...


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Force due to pressure over a given area is $F=AP$. A bubble will have three forces to consider. 1. Air pressure from air inside the bubble pushing the wall of the bubble outward (trying to make the bubble bigger) 2. Air pressure from air outside the bubble pushing the wall of the bubble inward (trying to make the bubble smaller), and 3. a surface tension of ...


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The boiling water will boil at a constant temperature. As long as the can is in the boiling water, you will not need to worry about the temperature of the stove. If this experiment is run at sea level, and you are using pure water, the can will remain at 100 deg C throughout the experiment. If you are at an elevation higher than sea level, and you want to ...


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Water, like most liquids does indeed get more viscous as its temperature approaches freezing point. See the graph below, which I took from the "Engineering Toolbox" However, what's interesting about this curve is that it does not diverge as $T\to 0^\circ{\rm C}$. The reason is that a phase change really is for all effective purposes a discontinuous ...


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Start by assessing the relative importance of each $Q$ term. Assume some order of magnitude values for the unknowns (based on experience and/or intuition) and see how big $Q_{lin}$ is compared to e.g. $Q_s$. Do that for all $Q$ terms and hope some will be negligible so they can be discarded. My guess is that $Q_{lin}$ and $Q_e$ are insignificant. You are ...


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That definition of temperature being average kinetic energy of all particles is colloquial. The information contained in specifying the temperature of any system is far more than what can be inferred from knowing the kinetic energy of all individual particles (if we can ever do so). Do realize that Temperature is a statistical concept while K.E. is not, ...


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At research laboratories where liquid nitrogen (and oxygen) are commonly used every day, closed containers of LN and LOx are routinely transferred and stored. These pressurized tanks typically operate at around 20 atmospheres and hold between 50 and 250 liters. For short-term needs and operations, the LN will be transferred to a vented vacuum-jacketed ...


2

I looked up the vapour pressuer of carbon dioxide at room temp (20 deg. C) and it is 57 bar, so I don't think you can have seen a cylinder of CO2 at 250 bar. If it is advertised as containing '250 bar' then the reality will be a lower pressure plus some solid CO2 in the bottle as well. For nitrogen, commercial cylinders can be supplied up to about 200 or ...


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"Thermal energy" is a bit of a misnomer because "thermal" really refers to a method of energy transfer, not energy storage. When energy moves from one system to another, it can do so via a thermal process (e.g. conduction, convection, radiation) or a mechanical process (something pushes on something else). So technically, I wouldn't call $\frac{3}{2}kT$ the ...



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