Temperature Definition and 1000 Threads

Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is colder or hotter.
Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have used various reference points and thermometric substances for definition. The most common scales are the Celsius scale (formerly called centigrade, denoted as °C), the Fahrenheit scale (denoted as °F), and the Kelvin scale (denoted as K), the last of which is predominantly used for scientific purposes by conventions of the International System of Units (SI).
The lowest theoretical temperature is absolute zero, at which no more thermal energy can be extracted from a body. Experimentally, it can only be approached very closely (100 pK), but not reached, which is recognized in the third law of thermodynamics.
Temperature is important in all fields of natural science, including physics, chemistry, Earth science, astronomy, medicine, biology, ecology, material science, metallurgy, mechanical engineering and geography as well as most aspects of daily life.

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  1. R

    Gas Mixture - Dew Point Temperature

    Homework Statement Only Number 1, not number 2 Homework Equations Dew Point Temperature T = Saturated Temperated at Vapor Pressure Partial Pressure = (mole fraction) x (Mixture Pressure) The Attempt at a Solution The dew point temperature is only dependent on the pressure of the water...
  2. guythreepwood

    Taking the temperature of a wire

    I'm new here, and I hope I'm posting this in the right place. My colleagues and I are trying to take the temperature of a steel wire as it's heated. We're heating it by putting a current through it. The problem we're encountering is that the thermocouple we're using to take the temperature of...
  3. wasup23

    I Introducing two identical containers with different gasses

    If you have two different containers filled with two different gasses at the same temperature, would they have less pressure when connected to each other? Dalton's law states that each of the gases behave independently when it comes to pressure as they fill the space as if they were the only gas...
  4. M

    Calculate the temperature of a wire as an electrical current flows through it

    Hey, so I'm just wondering what are the formulas needed to calculate the temperature of a wire after x amount of time as an electrical current is passed through it. I know how to solve for it... I just forgot the formulas. Thanks
  5. M

    Most efficient temperature to evaporate water?

    Hello, I have a question for you guys and gals. I am working on a Desalination project and am ironing out questions about efficiency. What would be the most efficient temperature to evaporate water? 50, 100, 110 degrees? Does it make a difference, or is the energy required to evaporate a fixed...
  6. alan

    Temperature and volume fraction of a liquid mixture

    I have known the interaction parameter of a certain liquid mixture which has the phase behaviour can be described by the lattice model. , is it possible for us to know the temperature at the critical point? Besides, if we know the temperature at the critical point, can the volume fraction of...
  7. P

    Coming up with a function to model expected room temperature

    I have some cubic box with light bulbs controlled by a dimmer. The dimmer is calibrated in degrees (0-270). I need help in coming up with a function that would accurately predict what the temperature inside the box would be after say.. 5 or 10 minutes. Basically, I need to come up with a...
  8. T

    Multiphase Flow in Fluid Dynamics - Energy Coupling

    Hello, I have a general question regarding energy coupling in multi phase flow. My question comes is based on the text from this book...
  9. J

    I Mass and temperature relation in stars

    Hoping someone can help me here, I'm only a student so I'm sorry if my question is badly worded. I'm doing my maths dissertation on a binary eclipsing star and I'm trying to work out the mass of one of my stars. I know the B-V value and effective temperature, and I believe the equation I need...
  10. CFurner

    Torsional strength at high temperature

    High school student here I am designing an experiment to test the effect of temperature on the torque required to twist a piece of metal, and need some advice on where to start researching. What I need help with is A) finding a table of the torque required to twist steel when cold, and B)...
  11. P

    Heat Transfer: Finding temperature at the junction

    Homework Statement A furnace is constructed with 0.5 m of fire brick, 0.15 m of insulating brick and 0.25 m of ordinary building brick. The inside surface-temperature is 1530K and the outside surface temperature is 525K. The thermal conductivities of the fire, insulating and building bricks are...
  12. MathematicalPhysicist

    A question on absolute kelvin temperature scale.

    I was asked in an exam the following question: Q: How is the absolute Kelvin Thermodynamic temperature scale defined ? My answer is the following: A: The absolute zero kelvin thermodynamic temperature is defined as the temperature for which the entropy of the system is zero, i.e ##S|_{T=0} =...
  13. P

    Thermal Expansion: Finding common temperature (Ring/Sphere)

    Homework Statement Find the common temperature at which the inner diameter of the ring is 0.05% larger than the diameter of the sphere. Given: Lead sphere d = 5cm To = 70°C ∝ = 29x10-6/C° Steel ring d = 4.9975cm (the sphere is 0.05% larger than the inner diameter of the ring, hence this value)...
  14. Emmanuel_Euler

    Medical Oral cavity temperature vs rectal temperature

    Hello Guys How are you?? Today i was studying physiology Body temperature measurement and i saw in general and in normal conditions that the oral cavity temperature is lesser than rectal temperature but why the oral temperature is lesser than rectal temperature?? And what is the reason?
  15. S

    Is the idea of negative absolute temperature analogous to a virtual image?

    Is the idea of negative absolute temperature analogous to a virtual image in geometrical optics? I was reading this article about such a negative temperature: http://www.livescience.com/25959-atoms-colder-than-absolute-zero.html It seems to me that since temperature is defined by its...
  16. anuraag

    Temperature Coefficient of Plain Carbon Steel Gr 1000 to 1095

    Dear Experts, I am looking for the variation of magnetic permeability of the plain carbon steel wire grade 1000 to 1095 with respect to the ambient temperature ranging from -40 deg C to 200 deg C. Any leads will be appreciated. Thank you!
  17. L

    Final temperature real gas behaving ideally

    Homework Statement Please consider a mixture of oxygen (1 mole), nitrogen (4 mole), and carbon dioxide (3 mole). The mixture was heated in a well - insulated vessel with 753 kJ. Determine the final temperature if the mixture is composed of real gases behaving ideally as described by Eq. 3.48...
  18. N

    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...
  19. Adam Bourque

    What’s the expected heating load as a function of temperature?

    Homework Statement Excel Table gives Temperature of Month & Avg NOAAtemp for bill Homework Equations y = mx + b (Assuming) The Attempt at a Solution 1) if we take temp of month as temp, linear model y=-0.1481*temp+124.8. 2) If we take temp for days of bill as temp, y=-0.1466*temp+124.74
  20. DaynaClarke

    Gas Compression Temperature Change

    Homework Statement "One way to heat a gas is to compress it. A gas at 1.00 atm at 25.0°C is compressed to one tenth of its original volume, and it reaches 40.0 atm pressure. What is its new temperature?" So, I have: P1 = 1 V1 = 1 T1 = 25 P2 = 40 V2 = 0.1 And I'm looking for T2 The question was...
  21. L

    Stress in a tube due to external radial temperature gradiant

    Hi everyone, To begin, sorry for my english...:S I try to calcualte inner/outer surface stresses on a pipe submitted to instanatenous temperature variation on the OUTER SURFACE. I know the Roark's formua giving the stresses but with an instantaneous temperature variation on the INNER SURFACE...
  22. T

    Maximum temperature reached by gas in expansion

    Homework Statement 1 mole of ideal gas with internal energy U= 3/2 RT , expands from initial volume Vi = 1/10 Vo following the equation p=(− po / Vo ) V +po . Find (a) the highest temperature reached by the gas during the expansion and (b) the maximum amount of heat taken in by the gas...
  23. R

    Difference between vibrational, rotational and electron temperature

    I am trying to explain the following statement in my own words... Would it be correct to say that.. I am unsure if a vibrational state is simply a different energy state or something more specific? Do the electron temperature, vibrational temperature and rotational temperature all...
  24. Borek

    Critical temperature, or: Is the supercritical liquid a phase?

    Somehow I am worried it is a can of worms, but I will still try. This started with a student confused with statements describing critical temperature for the gas/liquid equilibrium. Some books and sources state it is the highest temperature AT which it is possible to liquefy the gas just by...
  25. ervays

    -40 to 70C Degrees Special Refrigerator

    Hi all, I'm trying to find a special refrigeration device that can goes from -40 Degrees to 70 degrees. I need this machine for a laboratory to test sensors in differente temperatures. Does anyone knows where can I find something like that? Kind Regards Vicente
  26. Physics Dad

    Stellar Radius & Effective Temperature

    I have a question for my Astro homework and I am a little unsure as to whether I am going in the right direction Question Using an expression that relates luminosity, size and temperature of a star, and assuming all Main Sequence stars have the same mean density, determine the relationship...
  27. G

    Boil by increasing temperature or reducing pressure?

    Which one is cheaper to do if I have a reactor at 45 bar, 80C and wish to distill a substance before it enters another reactor at 15 bar, 150C?
  28. AndyCh

    B Some questions about terminology

    I thought this would be the most logical way to post this, but give me some grace if it is not because this is my first time posting on this site (then relinquish the grace and tell me how to do it properly haha). First: When a physics problem says "sliding past point P" does that mean it stops...
  29. Drakkith

    Newton's Law of Cooling When the Temperature of the Air Isn't Given

    Homework Statement You come across a dead body at 3 PM. Its temperature is 83.6 F. 30 minutes later its temperature is 78.6 F. How long was the guy dead before you found him? Homework Equations ##\frac{dT}{dt}=-k(T-Tair)## T(0) = 83.6 F T(0.5) = 78.6 F The Attempt at a Solution This is a...
  30. H

    A Hall coefficient's finite temperature experiments in metals

    There are lots of measurements showing strong temperature ($T$) dependence of Hall coefficient ($R_H$) in correlated materials (eg. cuprate superconductors and other oxide materials) and such plots are available in many recent experimental papers. However, I could not find any $R_H$ vs $T$ plot...
  31. C

    How to find mass given pressure and temperature

    Homework Statement A 3-m3 rigid vessel contains steam at 10 MPa and 500 degC. The mass of the steam is? I know this question involves using a thermo-table, I'm just very confused on how to find mass from the given information. Homework Equations Maybe PV=nRT The Attempt at a Solution I...
  32. ervays

    Temperature, humidity and gas sealed box

    Hi, I'm working on my thesis and I need to calibrate some gas sensors that I'm building. I need controlled conditions(temp, RH and a known gas concentration) in order to calibrate the sensors. I'd love to know some idea to make a sealed box in which I trace and vary those parameter. I've...
  33. Sheroff

    Which Pressure Gauge Determines Saturation Temperature in a Closed Loop Pipe?

    water is flowing in the closed looped pipe equipped with preheater. there are pressure and temperature gauges before the preheater and after the preheater. which pressure gauge should i use to know whether the outlet preheater temperature has reached the saturation temperature?
  34. Q

    I Temperature impact on laser emission

    Hi everyone, I'm trying to understand why laser diodes need a stronger input current to start lasing when their temperature increases. If I tried to add thermal transitions to the rate equations governing the evolutions of an atom quantum level populations (let's say ##n_{up}## and...
  35. T

    Calculate uncertainty in pressure, temperature and time?

    Homework Statement [/B] After doing a lab on air compressors, we were asked to calculate Error in Pressure, Temperature and time measurements taken (all at 30 second intervals). We took pressure and temperature values at time = 0,30,60,90,120,150 and 180 seconds. We repeated the experiment 5...
  36. Djok1234

    Help me to solve my house swimming pool temperature problem please

    What's up guys. Is there anyone who can challenge to solve this theoretical problem that can help to solve my house problem? There's an empty outdoor swimming pool that has width a, length b, and depth c, such as its volume = abc. The temperature of outside is -3 C° and we are trying to fill...
  37. D

    NTC and comparator to detect temperature trip point

    In "The Art of Electronics" the following is said: "A comparator in a circuit is a handy device that switches its output according to the relative voltages at its two input terminals. There is a temperature sensing device, a thermistor, which decreases in resistance by about 4%/°C. So we’ve made...
  38. F

    Skin temperature increase due to radiation absorption

    Hello, I am trying to figure out how much the human skin temperature would increase when the skin is illuminated by radiation of a certain intensity (W/m^2). We can assume that the skin has an emissivity and absorptivity both equal to 1. For instance, imagine the skin illuminated by the sun (I=...
  39. P

    How Does Entropy Vary with Temperature for Chemical Reactions?

    Homework Statement As you know it's finals time and I desperatly need help with one physics task (it's not my main subject, but I still have to pass it -.-). Here it is: According to data below count temperature-depended entropy and entropy itself for reaction: CH4 + 2 O2 = CO2 + 2 H2O CH4...
  40. Lacplesis

    Entropy and temperature question

    Hi folks, I have a question, I will first write down some old truths and then ask what is unclear to me. Now we know that Boltzmann's constant is the average kinetic energy of one molecule of ideal gas, related to its temperature T. The German scientist Clausius defined entropy change of some...
  41. C

    Equilibrium Temperature with three substances

    Homework Statement If a block of 250 grams of lead (specific heat (c) =130) at 315 degrees celsius is placed in a 200 gram aluminum (c=900) calorimeter cup containing 900 grams of water (c=4.1), and the calorimeter and the water are both initially at 15 degrees celsius, what is the equilibrium...
  42. Kara386

    Temperature fluctuations in helium

    I'm about to do an experiment on second sound in superfluid helium. Reading the lab manual it says we will generate it by putting a heater into the fluid and then passed an AC current through it. What we are going to measure is apparently the 'normal fluid fraction', which I guess under the two...
  43. G

    What is the equilibrium temperature of a collector plate?

    Homework Statement You would like to put a solar hot water system on your roof, but you're not sure it's feasible. A reference book on solar energy shows that the ground-level solar intensity in your city is 750 W/m^2 for at least 5 hours a day throughout most of the year. Assuming that a...
  44. ElPimiento

    Equilibrium temperature of some ice and steam

    Homework Statement "A well-insulated bucket of negligible heat capacity contains 120 g of ice at 0°C. If 20 g of steam at 100°C is injected into the bucket, what is the final equilibrium temperature of the system?" Homework Equations $$Q_{fus} = m_{water}L_{fus}$$ $$Q_{vap} =...
  45. BH1988

    Fe2O3 Thermal Decomposition Question

    Hi, I've been asked to heat a sample that contains Fe2O3, amongst some other things, to a temperature where Fe2O3 will decompose. I am unable to find the temperature at which I would need to heat the sample and I'm not entirely convinced this is actually possible with the equipment I have...
  46. Delta Force

    Temperature and Power Plant Output?

    This is probably a very basic engineering question, but I'm from an energy policy background and the resources I've found (such as this) are quite detailed. Internal combustion engines such as automobile engines and aircraft (jet and piston powered) produce more power in colder environments and...
  47. AliSkully

    Help with understanding equilibrium & temperature

    Can someone explain why when you increase the temperature on an endothermic reaction, it yields more products? Is it because the activation energy is higher in an endothermic reaction, so there is more time for the products to form? also why does decreasing the temperature yield more products in...
  48. D

    Why when I freeze a container does the humidity go down?

    I am working on a project to stockpile and freeze photographic film and paper for later use. This is not for academic or commercial purposes, but just for personal use. I've been experimenting and am stumped as t the following: I place a package of film in a ziplock bag in an environment of...
  49. A

    Finding Specific Heat of Unknown Metal

    Homework Statement I'm asked to find the specific heat of Metal X in this simulation: http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/thermochem/heat_metal.html Mass of Metal X = 120 g Temp of Metal X = 220 degrees Mass of Water = 30 g Initial Temp of Water = 20...
  50. T

    Lower kinetic temperature implies population inversion?

    I was just wondering: why does lower kinetic temperature imply population inversion? I've read this is true in a few (astrophysics) texts regarding molecular clouds, although this seems to be a more general result that I haven't really read an entire explanation for. Nevertheless, do you have...
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