# What is Tempeature: Definition and 37 Discussions

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1. ### B Ideas regarding gravity and entropy

I've never had any physics class before so please bare with me on my lack of understanding. I've been thinking about gravity and its relation to entropy lately and was wondering if my thinking is correct. Entropy seems to be an opposing force to gravity. where gravity is creating gradients...
2. ### How does the rise in temperature of fuse wire depend upon its radius?

I tried the following: We know, Q = mc (delta t) but by Joule's law of heating, we also know that H = I^2 R t Assuming that no heat is lost in the surroundings, we get Q = H => mc (delta t) = I^2 R t => (delta t) = (I^2 R t)/(mc) But m = V d = AL d and R = (rho L) / A => (delta t) =...
3. ### What is the temperature change of a bullet upon impact?

Summary:: What is the temperature change of a bullet upon impact. I have this problem to solve but I'm kinda stuck, would apricate any feedback. We fire a silver bullet with a muzzle speed of 200 ms−1 into a sack of sand. What is the temperature change of the bullet, if 40 % of its kinetic...
4. ### Temperature change in a gas expansion

1- ##\delta P_V =(\frac{\partial P}{\partial T} )_V \delta T_V## 2-##\delta V =(\frac{\partial V}{\partial T})_P \delta T+(\frac{\partial V}{\partial P})_T \delta P## so ##C_v \delta T=-P\delta V=-P((\frac{\partial V}{\partial T})_P \delta T+(\frac{\partial V}{\partial P})_T \delta P)## I can...
5. ### I Unplug Fridge During Below-30 Days?

Hi All, There have been a few below-30 days recently in many places in the upper hemisphere. Essentially, those days,we are putting food in the refrigerator to warm it up. If/when , say, 3+ days of below- 30 days are predicted, does it make sense to keep freezers on?
6. ### Ideal gas: Temperture at 1 atm

Summary: U=3/2*n*R*T Can some of you help me with this The total internal energy of an ideal gas is 3770 J. If there are 3 moles of the gas at 1 atm, what is the temperature of the gas? I use U=3/2*n*R*T but get the wrong answer, (101 K) but it should be 303 K [Moderator's note: Moved from...
7. ### Misc. How Can I Best Insulate a Safe to Protect Heat-Sensitive Materials?

Hello, I would like to ask you something about prevention from temperature equalization. I would really appreciate it if you can answer. To begin with, I want to store specific material into a breathable microfiber bag and place it inside a safe. This material is susceptible to heat and...
8. ### Understanding a simple statement regarding the measurement of temperature

Summary: 1.In the context of calibrating a scale to correlate volume change with temperature, my book states: "Since all substances change dimensions with temperature, an absolute reference for expansion is not available." What do they mean by an absolute reference in this instance? My...
9. ### Why is there no maximum temperature?

Given that absolute zero is the lowest temperature possible, were all particles have zero vibration. And given that the speed of light is the highest speed any object, particle, sub atomic or not can travel. Using 2 of the most fundamental laws of physics thermodynamics and general relativity...
10. ### Intro to thermal Physics - D. V. Schroeder -Entropy question

Hey guys, so I am reading this book and on pages 89-90, the author says: "Increasing temperature correspond to a decreasing slope on Entropy vs Energy graph", then a sample graph is provided, and both in that graph and in the numerical analysis given in page 87 the slope is observed to be an...
11. ### Probability at a temperature T that a system has a particular energy

Salutations, I'm starting in statistical mechanics and reviewing some related studying cases I would like to understand what occurs in small systems with normal modes of vibration, for example, a small system that has 2 normal modes of vibration, with natural frequencies $$\omega_1$$ and...
12. ### Temperature Measurement: Are All Thermometers Created Equal?

What is the difference in temperature with different thermometers for the same object? Thanks !
13. ### Temperature change in a vacuum?

Hello, I'm currently taking some summer classes at my college and was assigned a project to transport vaccines from one location to another (travel time ~2-5 hours.) We have to keep the vaccine within the range of 35-46 degrees Fahrenheit at all times. My group and I came up with the idea of...
14. ### A Planck 2015 CMB temperature individual pixel variance

Hi, I'm hoping someone can point me in the right direction please. I'm using the Planck 2015 CMB temperature (intensity) SMICA pipeline maps (Nside = 2048) and am trying to determine the temperature variance of each individual pixel. Variance and hit-count were provided with the 2013 CMB maps...
15. ### Temperature rise calculation for electrical devices

There are 2 types of temp rise measurement for electrical devices, 1)resistance type 2) thermocouple type (direct measurement) My query is 1) which method is superior and please explain me the reason. 2) Which gives higher value of measurement? Thanks in advance.
16. F

### Stationary temperature field inside a house

Homework Statement House: a room (see figure) has perfectly isolated walls, except the two windows where a convective heat exchange takes place (with the same transfer coefficient). Outside temperature in front of a sun-faced wall-sized panoramic window is T1, while at the back it is...
17. Z

### The Effect of Temperature on Magnetism

Hey guys, recently I have conducted an experiment investigating the effect of temperature (K) against magnetism (mT). I have found two formulas and understand that they are for both linear and non linear relationships but why does the function change from linear?
18. ### B Why Do Objects Glow? Exploring the Physics of Emission Spectra

well, this may be obvious for many of you guys here! and I know it must be! but I don't seem to find any satisfying answer online. well, I know that when you heat up any kind of matter it will emit light depending on its temperature, for example, humans will emit infrared light the same as...
19. ### Temperature ballance, two systems

Hi, I would like to ask you for advice with a problem, I'm working on. I have a regular shape object (glass cylinder) in which is the 100W heat source. The heat source is ind the middle of cylinder and radiates heat uniformly throughout it’s height. Heat, of course, gradually moving into...
20. ### Latent heat and specific heat in insulated container

Homework Statement A 1.0kg of ice at 0◦C, 3.0kg of water at 0◦C, and 5.0kg of iron at temperature T are placed in a sealed and insulated container. cFe =400J/ kg◦C ,cWater=4200J/ kg◦C , cIce= 2000 J/ kg◦C latent heat for ice is 3.3×105 J . The equilibrium temperature is 20◦C.Homework...
21. ### Partial Differential equation, Temp in a Cylinder

Homework Statement Homework Equations The Attempt at a Solution Because we are only looking at a cross section, I tried to reduce 5.3 down to just being a function of R and Theta. However I reasoned that there should be, based on this problem, no dependence on Theta either, so I figured I...
22. ### Temperature of Plexiglass due to laser strike

Hello, Any hep is appreciated. In the lab we want to use a 0.3mm sheet of plexi to reduce the intensity of the UV KrF laser. We want to determine the temperature of the plexi sheet after the laser beam strikes it. We have all the information about the laser... Is there a specific formula...
23. ### Deriving the thermodynamic beta from Lagrange Multipliers

I'm nearly at the end of this derivation but totally stuck so I'd appreciate a nudge in the right direction Consider a set of N identical but distinguishable particles in a system of energy E. These particles are to be placed in energy levels ##E_i## for ##i = 1, 2 .. r##. Assume that we have...
24. ### Thermocouple time to indicate temp

Homework Statement Homework Equations The Attempt at a Solution I do not know exactly how to start this problem. I would really appreciate it if you could give me some hints. I know that e^ - t/tau=T(t)-Twall/Ti-Twall where tau=m*cp/hA where h=convective heat tr.coeff and T(t) is desired temp...
25. ### I Does ice really melts if in conctact with reservoir at 0°C?

I came up with a basic doubt on heat exchange. Consider this example situation. A cube of ice of mass ##m## and at temperature ##\theta <0°C## is put in contact with a resevoir exactly at the temperature ##T=0°C##. The question is: does the ice melts, i.e. does the ice pass to liquid state? Or...
26. ### Determine inner wall temp of a pipe....

I have derived a few equations to determine temp distribution through pipe wall in subsea conditions. However I am finding it difficult to determine what the wall temperature will be. I need to know and use this temperature to further my analysis. As of now I know the following parameters...
27. ### Will Your Breath Condense on a Cold Winter's Day? A Homework Challenge

Homework Statement On a winter day, suppose your breath has a temperature of 30°C and a dew point of 28°C,and it mixes with the ambient air of temperature –10°C and a dew point of –11°C. Will you see your breath? Assume you are at sea level, and that your breath and the environment mix in...
28. ### Calculating Heat Loss in Long Pipe Transfer with Octave

Homework Statement Hello everyone, I hope that you guys could lend me a hand. I need to calculate the heat loss at any point over a long pipe while considering lambda of the pipe. I am trying to use octave to find a reasonable flow-rate to keep the temperature loss to a minimum at a reasonable...
29. ### Why is the logarithm of the number of all possible states of

Temperature of a system is defined as $$\left( \frac{\partial \ln(\Omega)}{ \partial E} \right)_{N, X_i} = \frac{1}{kT}$$Where Ω is the number of all accessible states (ways) for the system. Ω can only take discrete values. What does this mean from a mathematical perspective? Many people say we...
30. ### Equation for time to boil water? Some T over t dropping....

Hi, I am sorry I just forgot formula to calculate how long it will take to boiling water -> some lower temp. Thanks in advance.
31. ### Why Temperature Depends on Internal Energy, Not Pressure/Volume

Why temparature is only dependent on internal energy of something, say an ideal gas.
32. ### Convert Change in Temp from Celsius to Fahrenheit

Homework Statement Consider the apparatus that Joule used in his experiments on the mechanical equivalent of heat, shown in the figure below. Suppose both blocks have a mass of 0.69 kg and that they fall through a distance of 0.45 m. Homework Equations (a) Find the expected rise in temperature...
33. ### Calculating linear expansion of windshield 60cm*150cm

Homework Statement An automobile windshield has the dimensions 60cm by 150 cm. What minimum tolerance is needed in mm to prevent the windshield from breaking if the temperature changes by 200F (the linear expansion coefficient of glass is 9*10^-6 C-1) Homework Equations deltaL=alpha*Li*deltaT...
34. ### Tank of pressurized air to loosen bolts

Car mechanics use compressed air tools to open bolts. Instead of using an air compressor one can also use a tank of pressurized air. There is an air tank with a volume of 50 L to work with. The pressure of the tank is 50 bars when it is stored indoors at 20 °C. The bolt wrench needs at least 10...
35. ### Effects of Intermolecular Forces?

For a van der Waals gas, there are London dispersion forces causing the gas particles to be attracted to each other while the law of excluded volume provides repulsive forces. How do each of these characteristics effect the pressure, volume, and temperature of the gas? I assumed that for the...
36. ### Modeling of moist-adiabatic temperature?

Hi, I need to find some good article or book related to the modeling of this process: the parcel of air goes up from the surface to the top of troposphere ( to 12000 m ), we know the conditions at the bottom such as temperature, pressure and humidity, we assume that the parcel is isolated...
37. ### Pressure and temperature where volume is constant

If I where to take a volume of water that is at atmospheric pressure and then add more water molecules to it without allowing the volume to increase I understand that the pressure will increase but does this also mean the temperature will increase? My guess is that is does but I don't...