Thermal Definition and 1000 Threads

Homework Statement Interstellar medium is composed of atomic hydrogen at 100 K and number density 2E-7 m-3. Compute the average thermal energy density of the milky way disk. Then find the average magnetic energy density given the magnetic field strength of 3E-10 T. Homework Equations E=3/2 kT...

Homework Statement a) a styrofoam cup contains 200g of water at 20 C.What will be the equilibrium temp of the system after 100g of silver,initially at 300 C,has been added?you may assume that the heat capacity of the cup is negligible and that no heat is lost to the surroundings. (b) a further...

Hi, I am writing a MATLAB program to model the heat flow through space shuttle tiles. Does anyone know where I can find the thermal conductivity, density and specific heat of the different tiles on a space shuttle?

Why does the thermal decomposition of group 1 metals, except for lithium, yield a nitrite while that of group 2 metals yield oxides?

Hi there, I'm trying to clear up some misconceptions I have about emission spectra from various substances. Most of the discussion about gases focusses on the line emission spectra from a hot, low density gas due to electron shell transitions. But I also know that any charges that are made to...

Homework Statement A block of mass M is pulled at constant speed with force F a distance d across a surface. Using the energy principle, what can you say about the change in thermal energy of the block? a)...

Hi i am working on a research paper for which i need very good citation for the analytic analysis coupling Electric - Thermal-Structural physics(via Joule Thomson effect & Thermal stress/strain). Please provide any good source of mathematical relations describing the above complete or in part...

hallo to all, i use a Radiation Pyrometer to measure temperature and Radiation Trough a datalogger i get those measurements in Volt i am able to convert the Volt back in the temperature but in Radiation it is more difficult i found the Plancksche function, but i do not really understand that...

Hello I am trying to learn about the change of state between solids, liquids and gases but I don't understand exactly how it works. I've been reading material given by my school, but I got these two questions to ask because I can't answer them. These are not questions on the sheet they just...

Homework Statement A hair dryer consists of a coil that warms air and a fan that blows the warm air out. The coil generates thermal energy at a rate of 600 W. Take the density of the air to be 1.25 Kg/m^3 and its specific heat capacity to be 990J/Kgk. The dryer takes air from a room at 20C and...

Homework Statement A possible ideal-gas cycle operates as follows: (i) from an initial state (p1,V1), the gas is cooled at constant pressure to (p1,V2) (ii) the gas is heated at constant volume to (p2,V2) (iii) the gas expands adiabatically back to (p1,V1). Assuming constant heat capacities...

Hello, I have heard many times that red lighting is good for imaging applications where the effect of ambient light needs to be reduced to a minimum. What is the theory behind this? Why does red light (vs. other colors) reduce the effect of ambient light? Thank you.

MODERATOR NOTE: MISPLACED HOMEWORK, SO NO TEMPLATE When filling up the tub for a bath, only the hot water tap was turned on. After realizing the mistake after a minute with half the tub at 60 C, how much cold water (as fraction of the whole tub) at 9 C must be added such that the final...

I am looking to improve the thermal insulation on one of my favorite glass mugs. I am choosing between a silicone glove or a neoprene wrap. What is the difference between a silicone baking mat and silicone rubber? Does silicone or neoprene have better thermal insulation?

Hi, I'm doing a 1D thermal conduction simulation on Comsol Multiphysics 4.4 and my first component is vacuum. I did'nt found the vacuum in the material list. Should I create a new component with a null thermal conductivity ? Thanks

Homework Statement In thermal equilibrium, the particle in a gas are distributed in velocity space according to the Maxwell distribution f(v) = A*exp(-mv^2/(2KT)) What is the average velocity ? What is the most probable velocity ? Homework Equations <v> = ∫∫∫vf(v)d3v = (0 to infinty)...

Homework Statement a) Assume that a substance in a closed container is at thermal equilibrium with about half of its molecules in the gas phase and half of its molecules in the liquid phase. How could you use the Particle Model of Thermal Energy to explain which molecules are moving faster, on...

Hi, I am trying to design a tubular probe that's made of stainless steel (304), from what I've read it has a Thermal expansion coefficient of around 9.6 x10^-6 in/in/F give or take on the quality. I want to fill this tube halfway with an Epoxy, however from what I've read this epoxy has a...

Hi, my name is John and I am working on a textbook called Physics Syllabus Stage Six (PSSSix). I have done a draft of chapter 2, Thermal Physics. Although I have requested if this consultation is suitable for this forum, but yet been replied. This textbook is free (online definitely) or...

Homework Statement Hello, I have the following problem (an ABCD question): Two objects near each other are at the same temperature. Which of the following statements has to be true? A. The objects have the same internal energy. B. The objects have the same thermal capacity. C. No...

Recently there was an interesting thread on physics forum about possible uses of spent nuclear fuel. It seems to me that one of the problems with using decay heath from spent nuclear fuel is the low power density. This got me thinking that maybe with enough insulation the low quality heat...

Homework Statement The peak of the thermal radiation power spectrum (dR/dλ) is at a wacelength of about λm=hc/5kT. Why is the peak of the same power spectrum plotted as dR/df not at fm=c/λm= 5kT/h? Homework Equations dR/dλ= 2πhc2/(λ5(e(hc/λkT)-1)) f=c/λ The Attempt at a Solution

Hello everyone! First time asking a question here, go easy on me! I am a first year Mech-Eng student in Ireland, and I need some guidance from one of the amazing brains here at physicsforums. I am told by my thermofluids lecturer that in thermal expansion, the amount of material expanding is...

Homework Statement A python can detect thermal radiation with intensity greater than .60 W/m2. A typical human body has a surface area of 1.8 m2, a surface temperature of 30°C, and an emissivity e=0.97 at infrared wavelengths. What is the maximum distance from which a python can detect your...

I am trying to get a formula to estimate the heat lose in an airship. Is a mod for KSP, things that have into account: pressure, wind speed, temperature, air viscosity, thermal capacity of the atmosphere, gravity, etc. There are things that can be ignored as shape (or just use constant...

Imagine there is a semi-infinite semi-transparent body--such as a glass--at some temperature T. No surfaces exist. What is the energy intensity of thermally emitted light from any point in the body? If you use an absorption or emission coefficient (as I suspect is correct), can you explain how...

This is not a homework problem but rather a passage from my textbook that I don't understand. I don't think I quite understand the concept of reversible processes. Here is the passage from my book: "Consider a system in the quantum state s of energy Es. We assume Es to be a function of the...

Homework Statement This is not a homework problem but rather a passage from my textbook that I don't understand. I don't think I quite understand the concept of reversible processes. Here is the passage from my book: "Consider a system in the quantum state s of energy Es. We assume Es to be a...

Homework Statement Energy can be transmitted via radiation, the rate at which this happens is H=σAT4. A bar of iron is 0.5m long, 0.2m wide and 0.2m high. Iron has a density of 7900 kg/m3, a heat capacity of 400J/kgC, and a coefficent of linear expansion of 1.2x10-5 What is the rate at which...

I am looking Kaowool Thermal insulation for a project. It looks like the values presented are @2000 F, 1.28 BTU, .20 w/m*k I was wondering if someone could help me to figure out what the "output" heat would be at 2000 F. For example: If I have an aluminum rod sitting over a fire burning at...

Looking for some help here. If I have two objects, (1) a heat source that, let's say can get up to 1500 degrees, and (2) a simple metallic object, and let's say the object and heat source are relatively close to each other. Object number (2) has a small metallic probe that goes into the heat...

hello is there a good article or reference to outline the available methods to harvest ambient or solid thermal energy and their efficiency and limitations? thanks!

I am trying to figure out what the total thermal energy emitted by completely transparent matter. It seems Planck's law can't do this because the thickness or geometry of the mass is not given, only it's surface area. The spectral radiance of a black body is given by Planck's law...

I have a heat exchanger with water/air as medium and we test it in a facility where we cycle the water temperature between 25 to 95 degrees Celcius with a cycle time of 5 minutes for thermal fatigue. Our customer require the testing to be between 5 to 95 degrees instead with 3 minute long...

Homework Statement I need to find thermal stresses that will be produced in a tank barrel as a result of firing. First of all, I want to know if theses stresses can be small enough to be neglected? And if not, then how can they be calculated? I basically know the solution but I want to be sure...

So I'm not too sure about the answer to this question: explain why it is advisable to add water to an overheated automobile engine only slowly, and only with the engine running? So if something is overheating, it makes sense to want to cool it. Since the water's temperature is less than that...

Hi, The coefficient of thermal expansion for aluminium is 23ppm/C at 20C = 0.000023m per degree in temperature (C). Is this temperature: (1) the temperature of the air circulating around the material in the sun, (2) the temperature in the shade at that time of the day, or (3) the tactile...

Using kinetic theory, we can derive an expression for the thermal conductivity of a gas to be κ=nCmoleculeλ<v>/3 where n is the number density of the molecules in the gas, Cmolecule is the heat capacity of a single molcule (i.e the heat that must be given to each molecule to raise the...

A microtubule is 100 microns long. Take the young modulus as 1 GPa and the microtubule as a hollow cylinder with outer diameter of 12.5 nm and thickness 2.5nm. a) If one end of the microtubule is clamped down, and is the other end is free to wobble. Estimate the work that must be done to...

Hello everyone, First up, I know nothing about physics or chemistry. That out of the way, let's begin. I recently read about a very interesting material called Starlite which is supposedly a remarkable thermal barrier but is presumed lost to the world because the inventor kept the formula...

So you take some boiling water and drop a metal cube into it and the cube will reach the temp of the water. Or you leave some hot water out on a desk and the water will eventually become room temperature, right? Then why, in the summer time, does the inside of the car get way hotter than the...

I want to calculate the thermal stresses in the barrel of a tank. The barrel is smooth bore, auto-frettaged and chrome-platted. I want to know if the thermal stresses are small enough to be neglected and if not, then how can I find them? Relevant Equation: Thermal Stress= modulus * coefficient...

Hi, I'm facing a slight problem with getting a good version of the Schroeder: Introduction to thermal physics. According to my lecturer the newest 2013 international edition by Pearson (ISBN: 9781292026213) is not recommended, as it lacks some aspects. And anyway the course is built around the...

The "coefficient of linear expansion" (≡k) was defined in my book by the following relationship: ##\Delta L=Lk\Delta T## Where L is length and T is temperature I'm wondering, is this just an approximation? Because, if you were to increase the temperature by \Delta T and then calculate the new...

Homework Statement A spherical air bubble in a lake expands as it rises slowly to the surface. At the point it starts to rise, the pressure is 2.00 atm, the temperature of the water is 10.0 ∘C, and the radius of the bubble is 5.00 × 10^−3 m. At the surface, the pressure is 1.00 atm and the...

I have a conceptual misunderstanding it seems. Poisson's ratio is the ratio of elastic strain deformation of the transverse and longitudinal components. That being said, if I were to induce thermal stress (heating up) to a rod by keeping its ends (longitudinal component) rigid, would there be a...

Homework Statement A 3.50-kg block of iron initially at 8.00 × 10^2 K is placed on top of a 6.25-kg block of copper initially at 4.00 × 10^2 K. Assume the blocks are thermally insulated from their surroundings but not from each other and that they constitute a closed system. How much energy is...

The fastest way to transfer thermal energy would be through: A. Thermal radiation B. Thermal conduction C. Thermal convection D. Thermal induction I thought it would be thermal radiation, but my teacher said its conduction. Is he right? Please explain.

Homework Statement We have a pendulum in thermal balance with the surroundings - no damping. We measure the speed of the pendulum. The accuracy of each speed measurement is known. How does the accuracy of the speed change, if we decide also measure the position of the pendulum with accuracy 10%...

Hello I got to thinking about temperature when i prepared a lecture for my high school class. For a monoatomic ideal gas the temperature is proportional with the average kinetic energy of the atoms. For a diatomc gas we also have rotational energy (vibrations assumed to be freezed out), and for...