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. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. 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...
  12. 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...
  13. 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.
  14. 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...
  15. 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...
  16. 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
  17. 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...
  18. T

    Calculate temperature of a conductor

    Hello ! 1. Homework Statement i study for my exams. here is my current problem: a non-specific conductor is connected to an ideal battery (surrounding temperature: 20°C) and reaches a temperature of 24 °C . after cut in half it is again connected to the battery. what temperature does it reach...
  19. P

    Difference between using temperature in Celsius and Kelvin

    For one my homework questions I was asked to find the specific heat capacitance of a certain material. The specific heat capacitance has a temperature dependence given by: c = 0.20 + 0.14T + 0.023T2 the units for T is temperature in Celsius and c is measured in cal/gK. 2.0 g of the material was...
  20. M

    How Do You Convert Body Temperature from Celsius to Fahrenheit in Statistics?

    Homework Statement (1) Let the random variable X be the body temperature in ◦C for a randomly chosen person during waking hours. X is assumed to be a normally distributed with mean E(X) = 37.5 and standard deviation sd(X) = 0.3. Let Y be the body temperature in ◦F for a randomly chosen person...
  21. Battlemage!

    B Albedo, atmosphere, and predicted temperature of Venus

    The reason I am making this thread is because I have a question regarding predicted temperatures of planets based on their area, distance from the sun, and albedo. Going by the planetary equilibrium temperature, T4 = [L(1-a)]/(16σπD2), I have seen numerous websites state that Venus would...
  22. A

    B Temperature of an accelerating system

    if i take a box and fill with solid metal that has a temperature T . what if the box is accelerated to the speed of light . would T -> 0 ?
  23. Aafia

    What is the effect of temperature on enzymes in poiklotherms

    Since enzymes have particular temperature on which they are able to catalyze the reaction and increasing the temperature above optimum can damage enzymes then how does poiklotherms survive as they change their body temperature according to environment unlike homoiothems. Also wouldn't their...
  24. Omish

    What temperature do thermocouples show? Static or Total?

    What temperature does thermocouples show? Static or Total? And also in formulas for example Q(dot) = m(dot) * C_p * (T2 - T1) which temperature should be used precisely?
  25. R

    Why the temperature of a moving jar of gas doesn't increase

    Homework Statement Why doesn't the temperature of a moving jar of gas increase? Homework Equations Average KE is proportional to temperature The Attempt at a Solution This is just an extension of a problem my friend sent me, and I'm stuck on why even though average velocity is increasing...
  26. E

    Book of T-S diagrams, or the like

    Hello - I just starting out in chemical engineering. I hold a batchelor's degree in Chemistry, and am making a transition to ChemE. This isn't for any class, just in general for reference, does anyone know of a good book that is primarily just thermodynamic charts, like T-S diagrams? I have...
  27. I

    Constant heat flux or constant temperature

    Hey all, first time posting! So I'm having trouble with understanding the differences between the constant heat flux and constant temperature condition when not in a textbook. Some research I have begun working on involves a strip of heat tape sandwiched between two aluminum plates which are...
  28. P

    Low temperature production with compressed air

    Suppose, there are two cylinders of compressed gas, say air. Both are at same temperature and pressure and the amount too is same. Now, contents of both are released but in a different way. One has been released directly and the other has been released through compressed air turbine having a...
  29. G

    I Exploring Time Dilation: The Effects of Temperature on Clocks

    Hi. Temperature is movement on a microscopic scale, and movement leads to time dilation. So what happens if we heat up a clock? Let's for example assume a pendulum with negligible thermal expansion, such that all other thermal effects on the period can be neglected. Will it run slower? What...
  30. C

    Can I Calculate Temperature Release from Energy Change in a Body?

    Hi, I would like to ask a question, if I may: if I have a body with a calculated Inertial moment at time t0, that in a space of time delta t changes, there's a variation in its kinetic energy, right? How can I calculate the released temperature in that elapsed time? Is that energy all lost in...
  31. C

    Calculating Temperature Change from 20°C to -20°C: Homework Question

    Homework Statement in this question , it's not stated that whether the temperature change from 20°C to -20°C or -20°C to 20°C . I'm confused... Homework EquationsThe Attempt at a Solution I think it should be changing from 20°C to -20°C so delta T = (-20-20) = -40°C , am i right ?
  32. M

    Temperature of a radioactive material

    Hi all! I have a certain quantity of a radioactive material (e.g. 1 kg) in the open space. How can I calculate the temperature of this material as a function of time? If it is useful, we can consider a beta decay material. Thanks a lot.
  33. E

    Temperature Coefficient of Resistance and Specific Heat

    I am trying to estimate the amount of electrical power needed to heat up a material from 20C to 1000C in 20 seconds. Assuming it is 18sqin and 3mm thick, I used the specific heat which was given as 0.78 J/gC and weight 11.39g (from the destiny of 3.26). 0.78 J/gC x 11.39g x (1000C - 20C) /...
  34. shina

    Time & Temperature: Proportional or Inverse?

    Hey I m new here. I hope u all will cooperate with me. As I have read much about proportionality in science. So can I say that when time increases temperature also inreases or decreases. So time is proportional or inversely proportional to temperature.
  35. T

    Why the temperature remains constant at the boiling point?

    Why all liquids vaporize on boiling point instead of the temperature gradually increasing along with vapor pressure and more liquid atoms evaporating? Does it have anything to do with formation of vapor bubbles?
  36. C

    Change in length due to temperature

    Homework Statement in the notes , i was told that ∂A is the resistance of aluminium rod...I'm wondering the change length of steel rod that we can 'see' is ∂ st or ∂T(st) ? Homework EquationsThe Attempt at a Solution I think the change length of steel rod that we can 'see' is ∂ st ?
  37. Niladri Dan

    Temperature in Space: The Kelvin Scale

    The Kelvin scale states that the temperature is a measure of the kinetic energy of the particles(molecules) of the system. But what is the temperature of a system where there are no particles...for example free space, far away from the stellar civilisation...
  38. D

    A Carrier concentration temperature dependence; semiconductors

    Hi all, I'm reviewing device physics and I would like to understand how majority and minority carrier concentrations for both N- and P-type substrates change with temperature. My reference, Pierret's Semiconductor Device Fundamentals, has this figure: and I want to generate curves for all...
  39. T

    Calculating combustion temperature of mixture

    Hey guys, I'm trying to write a small article that very simply explains some of the math involved with a rocket engine. I'm not looking for a very accurate answer so I tried the following method 1) Stoichiometry on the fuel which was sugar and saltpeter and their respective enthalpies of...
  40. E

    How to calculate blackbody temperature from radiance band?

    I know how to calculate blackbody radiance in a spectral band from a temperature by integrating (or summing) planks function. How can I do the reverse? For example, I have a Radiance of 1000 W/m^2/sr in the 3-5um band, I'd like to be able to calculate 666.6K.
  41. S

    Calculating heated rectangle temperature rise

    Hi I have a question about temperature rise and thermal conductivity. If I have a small 1 watt heater (3 x 3 x 3mm) in the middle of a rectangular block (100x40x70mm) made of a material that has a thermal conductivity of 0.48W/mk, how do I work out the final temperature that the block settles...
  42. G

    Robotics Engineers -- How could a bot navigate by temperature?

    I've seen a bit of research that relies on imaging methods like FLIR for input. My question adds a couple wrinkles: How could a robot Navigate without imaging? I.e., using only local sensors like a thermocouple or array of thermocouples. Extract navigation info from turbulent thermally...
  43. P

    I Determine the temperature of a star via its spectrum

    In the following video (, diagram also given for reference), the professor says that if the graph peaks in a short wavelength, then the star is a hot star (or galaxy) and if it does so in a long wavelength, then it's a cold one. However, I fail to understand this. How does it happen that if a...
  44. Magnetic Boy

    Bosons at very high temperature

    Will all particles be in excited state in boson condensate if temperature approach infinity?
  45. A

    Thermo: Principles behind temperature drop across a valve

    Hi everyone Would like some help here. If I draw a control volume across a valve that I can control the flow area to, and I know the temperature and pressure upstream of the valve, I will know its enthalpy:in. High temperature liquid going through this valve supposedly changes to steam due...
  46. S

    Internal energy in irr. process with molar heat not constant

    I'm a bit confused about the following situation. In a irreversible thermodynamics process the molar heat of an ideal gas changes according to a function of the temperature, say ##c_v=f(T)## (which also leads to ##c_p=R+f(T)##) and I'm asked to determine the heat exchanged during that process...
  47. A

    I Why does temperature always rise in stars?

    Hello everyone, I know that pre-main sequence stars do heat up because of gravitational contraction, and the increase in internal energy (and so in temperature) comes from this shrinking and is governed by the virial theorem (...
  48. S

    Thermal expansion of liquid in a tube

    Homework Statement A cylindrical glass tube (linear thermal expansion coefficient ##\alpha##) contains liquid (volume thermal expansion coefficient ##\beta##). The height of the tube is ##h_{t,0}## and the height of the liquid inside of it is ##h_{l,0}##. If the temperature changes of an amount...
  49. S

    Engineering Moving Mechanical structures: stress, wear, temperature....

    Hi! I am looking for a textbook that explains/describes for moving mechanical structures (such as linkage mechanism, engines, ... and not buildings, bridges, ...) the stresses, deformation, wear, temperature change, ... due to operating. E.g. Linkage mechanism: what are/defines the stresses...
  50. J

    I What is the relation between Temperature and Quantum State?

    Hi folks, Let's pick a simple example, the H atom. We can calculate all spherical armonics, all quantum numbers so we are able to know which are all the possible states of the electron. We know all the values this observables can take. But the question is, let's say we have a handbook of...
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