What is Temperature: Definition and 1000 Discussions

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. N

    Calculating Internal Energy & Temperature Change of Ideal Gas

    Homework Statement What is the change in internal energy (in Joules) of an ideal gas that does 4.675x10^5J of work, while 2.95x10^6J of heat is transferred into the system and 7.95x10^6J of heat is transferred from the system to the environment? Calculate the change in temperature of the two...
  2. Chadi B Ghaith

    I Find Oven Temperature at various moderate mode?

    Hello, I want to convert gas unit into oven temperature (Fahrenheit, Celsius). Which formula I can use? Also I want to know at which oven temperature we can assume it as moderately high or cool temperature??
  3. onargaroberts

    Impact of the engine thermostat temperature setting on engine efficiency

    Will a four cycle, internal combustion engine have greater thermal efficiency with a relatively cool jacket water temperature, say 160 degrees F, or a relatively hot water jacket temperature, say 190 degrees F? These specific numbers are only important in as much as they are commonly available...
  4. D

    Electromagnetic Radiation temperature

    Is there a meaningful way to convert the energy of an electromagnetic wave to a temperature? I mean this more along the lines of how the universe has a temperature of 2.7 kelvin due to electromagnetic radiation. I'm honestly just curious to determine the temperature of the universe after nearly...
  5. B

    Thermal expansion of a pipe with wall temperature gradient

    I have a pipe holding liquid at 80°C. The outside atmosphere is -2°C. The pipe gets a temperature gradient over the wall thickness. The outside fibers will thus restrain the inner fibers from expanding. I would like to know the increase in the inner dia of the pipe. I have found temperature...
  6. A

    I Unruh effect, temperature and particle density....

    Hi all, This is a followup to a question I asked a number of years ago about the Unruh effect. I understand that an accelerated observer will see warm gas of particles following a blackbody distribution with some temperature T, where as an inertial observer would see none. My question is: how...
  7. P

    Temperature as a function of vibration energy quanta

    Homework Statement Consider a small cluster of four copper atoms. Assume, that each atom can oscillate around its equilibrium position independently of the other atoms. Let us model each direction of vibration as a harmonic oscillator, whose energy is quantized Evib = ¯hω(n +1/2), where ω =...
  8. Edward258

    Find the temperature increase of a rotating disk

    Homework Statement It's a Blackbody radiation problem: A beam of wavelength λ, in the state of right circular polarization, leads to an absorbent disk.The mass of the disk is m, it's specific heat is C, and its moment of inertia is I .The disk is initially at rest, but after a lapse of time...
  9. Kara386

    I Why does LED band gap decrease as temperature increases?

    I've tried to summarise the explanation my professor gave. Is it correct or have I misunderstood? It's a highly simplified view of things anyway, but here goes: Taking the simplest 1D case, there are two possibiities for an electron in the lattice: it may be scattered and move back the way it...
  10. ShayanJ

    A Near horizon limit and Hawking Temperature of the horizon

    One way that people introduce the Hawking temperature of an event horizon, is by taking the near-horizon limit of the BH metric and then do a Wick rotation of the time coordinate. Then, the regularity of the metric requires that the Euclidean time to be periodic. But how can this give us the...
  11. N

    Final temperature after pouring soda into glass with ice....

    Homework Statement Soda from a ms=12 oz can at temperature Ts=13 degrees C is poured in its entirety into a glass containing a mass mI=0.16kg amount of ice at temperature TI=-19.5 degrees C. Assume that ice and water have the following specfic heats c1=2090 J/(kg*C) and cs= 4186 J/(kg*C), and...
  12. H

    How to determine temperature of filament?

    I was wondering in class today how I could determine the temperature of a filament in an incandescent light bulb? Mainly then so I could determine the thermal energy outputted through radiation. So after school I used a test circuit. I started with the Stefan-Boltzmann law which is Q =...
  13. G

    Finding Average Temperature Using Boltzman Constant

    Homework Statement Deep in space, there is a particle density, p, is 1.01cm^-3. Pressure is extremely low, P, is 5.1 x 10^-17 N/m^2. What is the average temperature of mostly empty space? Answer in K Homework Equations T=P/pKb The Attempt at a Solution I plugged in...
  14. Monsterboy

    To find final temperature when an evacuated bottle is opened

    Homework Statement The internal energy of air is given, at ordinary temperatures, by ## u= u_o + 0.718t ## where ##u## is in kJ/kg, ##u_o## is any arbitrary value of ##u## at 0oC, kJ/kg, and t is temperature in oC. Also for air, ##pv= 0.287(t+273)## where p is in kPa and ##v## is in m3/kg...
  15. Akmalidin

    Battery temperature while charging

    Hello, I am made a powerbank myself with li ion battery. I used boost converter and everything is fine, charging my phone. But the li ion battery and my boost converter is getting really hot while charging my phone.The battery capacity is 4400mah. I don't know the reason for such temperature...
  16. Kaneki123

    Effect of Temperature on Solubility

    Solubility of some some solids decrease with increase in temperature...There is an exothermic reaction so a lot of heat is produced in the solution...My question is that why does solubility decrease?...Any increase in temperature (the heat we provide) should just excite the molecules more and...
  17. Selveste

    Temperature dependent heat-conductivity

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  18. A

    Could a good conductor be heated past the temperature of....

    Could a good conductor, like some metal, be heated past the temperature of the heat that's heating it. Like if I use a 100 degree flame and hold it for hours on some piece of metal, could the metal go above 100 degrees? And I'm not talking about special cases. I mean does this generally happen?
  19. Galbi

    Water evaporation by negative pressure and 0% of RH

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  20. W

    Statistical definition of temperature

    hello everyone. i need help understanding this statement: d(lnΩ)/dE = 1/kbT so Ω are the posible microstates for energy E, and the derivative of Ω w.r.t E is 1/kbT. why? what i understand so far is: looking at the division of energy of two "connected" systems the energy will divide itself in a...
  21. M

    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...
  22. J

    How to calculate time to change the temperature of metal

    So I'm looking to calculate the time required to raise the temperature of a piece of lead. What I know so far: Mass of metal: 4 grams Initial temperature: 250 degrees Celsius Final temperature: 350 degrees Celsius Specific heat of lead: 0.13 kj/kg I'm very new to thermodynamics and don't know if...
  23. F

    Temperature of two bodies in the same room and under the Sun

    Hello Forum There are three different mechanisms to transfer thermal energy: conduction, convection and radiation. It is well known that when two objects having different temperatures T1 and T2 are in contact, they will eventually reach a common intermediate temperature (the weighted average...
  24. M

    I Calculating LED Efficiency with Radiant Power and Temperature

    i wonder if it is possible to get the efficiency of an LED just by knowing the radiant power an the outside temperatur. i also know the temperatur of the emmited light. well they say the LED has an efficiency >1 because it takes heat from the out side and turns it into rays. so these two things...
  25. A

    Thermodynamics/ Heat,volume and temperature

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  26. I

    Temperature inside a box as particles escape a small hole

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  27. Riverbirdy

    Solving for temperature and volume of Dietrici Equation

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  28. A

    Does heat from drilling cause damage to drill bits?

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  29. victorhugo

    Air friction and speed & temperature

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  30. G

    Calculate the Flame temperature

    Homework Statement A fuel gas consists of 75% butane (C4H10), 10% propane (C3H8) and 15% butene (C4H8) by volume. It is to be fed to the combustion chamber in 10% excess air at 25°C, where it is completely burnt to carbon dioxide and water. The flue gases produced are to be used to generate 5...
  31. sliperyfrog

    Ideal gas law, Find the Temperature of the container?

    Homework Statement [/B] There is a lid on a .25m diameter, .30m tall cylindrical container enclosing .021kg of air. The lid is held in place solely by atmospheric pressure. It take 220N of force to pull of the lid at an atmospheric pressure of 101kPa. What is the Temperature of the enclosed...
  32. A

    What is solidus and liquidus temperature of granite?

    My understanding is that because a rock is composed of variety of minerals, so it does not have fix melting point, rather there is a range below which whole rock is solid and above which whole rock is liquid. I want to know this liquidus and solidus temperature for granite rock based on pressure...
  33. arpon

    Temperature dependence of Cv at very large volume

    Homework Statement In the case of a gas obeying the equation of state $$\begin{align}\frac{Pv}{RT}&=1+\frac{B}{v}\end{align} $$ where ##B## is a function of ##T## only, show that, $$\begin{align}c_v&=-\frac{RT}{v}\frac{d^2}{dT^2} (BT)+\left(c_v\right)_0\end{align}$$ where ##\left(c_v\right)_0##...
  34. supak111

    Energy release from 75c drop in water temp, 1L?

    Hey everyone can anyone tell me how much energy is released (joules) if you take 1 liter of water at 100C and drop it down to 25C (room temp, reg pressure)? Is it significant amount? Better even how much energy is released (approximately) for every 1c drop in temp? Is the release in energy...
  35. xunxine

    Temperature change in different containers

    Homework Statement This is a question for 10 year old but I have a problem understanding why the answer is so. (The student asked me this.) There are two similar containers, X and Y, with 500 ml of boiling water. X is an aluminium container. Y is a plastic container. They are then covered with...
  36. Pao44445

    How Does Temperature Affect Copper Wire Resistivity?

    Homework Statement Initially, copper wire is 20oC then raises the temperature of the wire casing the resistivity up 12%, find the temperature at the final. Homework Equations R=Rref[1+α(T-Tref)] The Attempt at a Solution I am completely confused with this mathematics problem,Stucking with...
  37. A

    Gas Pressure vs Temperature moved between containers?

    I have a question regarding an occurrence with Nitrogen gas and two separate containers. I'm trying to explain why when I fill my steel pressure vessels to ~180psi on an avalauncher from a larger 2000psi steel tank, the pressure slowly drops to ~175psi after the fill. I believe this to be...
  38. moenste

    Find initial current and resistance in a circuit

    Homework Statement A battery of internal resistance 0.50 Ω is connected (as shown below) through a switch S to a resistor X, which is initially at 0 °C. When S is closed, the voltmeter reading falls immediated from 12.0 V to 10.0 V. The reading then rises gradually to a steady value of 10.5 V...
  39. B

    I How Can Exponential Decay Reveal Initial Temperature?

    Suppose that you take a thermometer outside where it is 100°. T(5min)=80° T(15min)=90° What is the initial temp of the thermometer? Given equation dT/d t= k(T-Te) Derived Equation ⌠(T-Te)^-1 (dT/dt)dt =⌠ kdt ln(T-Te)=kt + c T=ce^kt + Te so i basically got the answer by knowing c...
  40. P

    How much reduction in temperature can be achieved?

    I want put here an imaginary, but close to reality scenario. We have 3 MW power plant here having 1800 kg/hr or 0.5 kg/sec steam flow and the exhaust will be steam at 1 bara pressure and 100C temperature. If a cooling system of 2000 ton capacity is fitted to the Condenser, how much it can...
  41. T

    Sub Zero Temperature Chamber (around -50°C.)

    Hi Guys, Thanks for looking at the post firstly. I'm in the process of creating a chamber roughly around 30mm x 50mm x 70mm (W, L, H). The chamber will be used below the typical refrigeration temperature (-18°) of around -50°C. Please could you offer some advice where to start with this. 1...
  42. D

    Temperature in the regulator valve of a cylinder

    Homework Statement There is a cylinder of oxygen connected to a valve (A) and then to connected to a regulatory valve. The volume of both valves and the pipes between them is Vr and can be disconsidered in regard to the cylinder's volume. The oxygen can be considered a perfect gas with...
  43. I

    Constant pressure specific heats when temperature changes

    Homework Statement Im trying to understand what would be the correct approach for calculating the constant pressure specific heat for an ideal gas undergoing a process where the temperature is changing. The reason I am asking is because the equation used to calculate Cp0 is dependent on the...
  44. R

    Absolute temperature for average translational kinetic energ

    Homework Statement The ammonia molecule (NH3) has a dipole moment of 5.0×10−30C⋅m. Ammonia molecules in the gas phase are placed in a uniform electric field E⃗ with magnitude 1.3×106 N/C . Part A: What is the change in electric potential energy when the dipole moment of a molecule changes...
  45. P

    If something moves fast it gains temperature?

    Temperature is the average of the kinetic energy of the particles, if the bunch of particle moves fast and you look at the particles in two differece frame of reference, on steady with the bunch of particles and the other not, in the last one you get an higher temperature of the bunch of...
  46. wolram

    B What is the initial temperature of the Big Bang?

    We all know that the temperature of the back ground radiation is 3k, but how have we calculated the intiial temperature of the big bang.
  47. Deebu R

    Temperature at the junction of 2 wires

    Homework Statement The thermal conductivity of copper is 4 times that of brass.Two rods of copper and brass having same length and cross section are joined end to end. The free end of copper is at 0 degree C and the free end of brass is at 100 degree C. The temperature at the junction is...
  48. Z

    Why isn't the temperature of this vapor T_sat?

    A rigid tank with a volume of 2.00m3 contains 5.77 kg of saturated liquid-vapor mixture of water at 75 deg C. Now the water is slowly heated. Determine the temperature at which the liquid in the tank is completely vaporized. Why isn't the temperature just 75C? If it is already a mixture in...
  49. falcon555

    Silicon resistance change with temperature

    Good day everyone I'm doing a homework and stuck on the parts ii, iv and v. In fact I don't know the formula to calculate them Could someone help me to solve them, please
  50. Z

    Why can we assume the temperature of a fluid is T_sat?

    For example, in this question.. A 11 L rigid container contains 10-kg of R134a at 100kPa. Determine the temperature and total enthalpy in the container. Why can we just assume that the temperature we're looking for is T_sat, how do we know this isn't a compressed liquid? How do we know it...
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