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. J

    Unsure Regarding Temperature Model for an Open System

    Hi guys, I am currently working on my master thesis. I am supposed to make a dynamic model for a gas system and have some trouble setting up the energy balance. I am a noob when it comes to uploading pictures, so I don't have a figure for this, but let's consider a general control volume (CV)...
  2. V

    Thermodynamics Final Temperature of Water

    Homework Statement A certain mass of water in a copper pot is heated over a stove that releases joules of heat to heat the water. Later the same mass of water in an aluminum pot is heated over another stove that releases the same amount of heat in order to heat the water. Then the water in...
  3. AlexanderinCbus

    Question from a layperson: Particles & temperature

    Hello! First post here so go easy on me. I am a Physics enthusiast, but I fear I am a layperson when it comes to the field. Most of what I know comes from low level college classes and the youtube channel PBS Spacetime. I have a question that might be a ridiculous one. But here goes. (Go easy...
  4. M

    Questions about Subsolar Temperature

    1. The problem statement, all variables, and given/known data I'm having a little trouble understanding planetary subsolar temperatures. The first equation comes from viewing the absorbing and radiating areas of an object as the same and the second equation comes from viewing the absorbing area...
  5. B

    Velocity in microchannel with temporal temperature variation

    a microchannel of length 2L and width h in the thermal cycling region. the temperature profile ...(1) the cyclic temperature profile leads to a time dependent density ...(2) using the mass conservation equation i.e. ...(3) and momentum balance equation i.e. ...(4) we have to find the exact...
  6. M

    Calculating Temperature Change for Heat Exchanger

    Hello, After the last post I completely changed the system. I now have a new system. Based on the feedback from last time I increased the time in contact with the block significantly. And I have made it a two stage unit. Here are the parameters for the first stage. An Aluminum block. (assume...
  7. R

    Can dissolving minerals affect water temperature?

    Are there any type of minerals/molecules/elements even solids that when dissolved, in say a glass of room temp water, can raise or lower the temperature? Examples...
  8. M

    Maintaining Magnetism at High Temperature

    The only way for me to move 1200 degree steel is with a magnet. The magnet loses its magnetism at 800 degrees, though, causing some pieces to fall and potentially injure people. Is there a way to electrically boost the magnetism of an existing magnet, apply an additional field to the magnet...
  9. H

    Ideal Gas Equation and Temperature change?

    During a thermodynamic process, the state variables of an ideal gas, measured in kPa, m3, and oC, varied in the following way: P2 = 2P1 V2 = 3V1 T2 = 8T1 What is the temperature increase of the gas, T2 −T1 ? I've been given an answer of 4780 and I'm not sure how to get there?
  10. EastWindBreaks

    How to find internal energy with constant temperature?

    Homework Statement since specific heat c changes with temperature, but its treated as a constant in the heat formula, so that means that heat formula Q=mc(T2-T1) is just an approximation? correct? I see some texts define heat as Heat, q, is thermal energy transferred from a hotter system to a...
  11. EastWindBreaks

    How to find internal energy with constant temperature?

    since specific heat c changes with temperature, but its treated as a constant in the heat formula, so that means that heat formula Q=mc(T2-T1) is just an approximation? correct? I see some texts define heat as Heat, q, is thermal energy transferred from a hotter system to a cooler system that...
  12. J

    Pressure, Volume, and Temperature at a Point in a Thermodynamic Cycle

    Homework Statement Question: https://imgur.com/a/8rUw1 Graph: https://imgur.com/a/Z1oBO Homework Equations Answer for Q1 (Just the formula) : https://imgur.com/a/uesqN The Attempt at a Solution I have realized that from 1-2, there is an increase in pressure, decrease in volume and increase...
  13. T

    Temperature and magnetic flux density

    Hello all; I am new in this forum, currently in High School. For some time now, I have been looking online for a relationship between temperature and magnetic flux density of a ferromagnet; below the Curie point. However, I can't seem to find any relationship or formula. Do any of you know...
  14. S

    Saturated VapourPressure of Steam above Critical Temperature

    Hello all, I am not sure my question will totally make sense for those of you who now this topic well but as I am new to it I hope I can be forgiven. My problem is to work out how much water will condensate as a stream of moist air is expanded through a turbine. So far I was using Antoine's...
  15. M

    How long does it take to heat a vessel?

    Homework Statement I need to find the time it takes to heat a vessel of water which is closed. Here is what I have: Specific heat capacity of water: 4184 J kg^-1 K^-1 Density of water: 1000 kg m^-3 Volume of water added and volume of vessel: 500 L or 0.5 m^3 Heat capacity of the vessel: 91000...
  16. K

    Why Does the Chain Rule in Thermodynamics Include a Negative Sign?

    I'm trying to understand why $$\left(\frac{\partial P}{\partial T}\right)_V = -\left(\frac{\partial P}{\partial V}\right)_T \left(\frac{\partial V}{\partial T}\right)_P$$ where does the minus sign come from?
  17. N

    B Do temperature and gravity affect particle or nuclear decay?

    I thought of another question(s) :) does temperature affect the rate of the decay at all? Does temperature effect the energy of the decay; in that the energy of the electron anti neutrino would be higher?
  18. K

    Calculating the maximum temperature of a heating wire

    <mod: moved from intro> Hello all! This is my first post in this forum. I am struggling with the following question regarding a hair dryer. The hairdryer can be seen as a cilinder with a fan inside blowing air at speeds from the table below and 1 nichrome wire which heats up consuming different...
  19. S

    Liquid temperature under pressure

    Hello, I have a question regarding bath pasteurising cider in bottles. The bottles are carbonated with CO2 and capped, I heat the water up to a temperature of 70deg.C I use a test bottle filled with water and with a cork in the top, I use this to monitor the temperature inside the bottle. So my...
  20. Muthumanimaran

    What is the Maximum Temperature for a Copper Block at 1000 atm Pressure?

    Homework Statement (a) A block of copper at a pressure of 1 atm and a temperature of 5 degree celcuis is kept at constant volume. If the temperature is raised to 10 degree celcius what will be the final pressure? (b) If the vessel holding the block of copper has a negligibly small thermal...
  21. 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...
  22. E

    Write a function that will find a temperature....

    Hi everybody, I seem to be having trouble coding a function that returns the integer value at which degrees celsius is equivalent to degrees fahrenheit. Here is the question: Write a function that will find a temperature that is the same in both Fahrenheit and Celsius. First define two...
  23. U

    Somewhat Complicated Thermal Problem

    Problem Description: I have a solar panel of some surface area, material, and thickness mounted to an enclosure. The panel is isolated from the enclosure at some distance with a multitude of materials (air, insulation, plastic, metal) between the back surface of the panel and interior volume...
  24. F

    Energy of an ideal gas given its multiplicity

    Question: The multiplicity of an ideal gas is given by g(U) = A.U3N/2, where U is the energy of the gas, A is a constant and N is the number of particles in the gas. Prove that the energy of the gas given a temperature T is U = (3/2).N.kb.T Attempts: My first thought was to...
  25. Sveral

    Cutting magnets without losing magnetization (Curie temperature issue)

    Hello, I wanted to know, if someone knows of a realistic option of, how to cut barrium ferrite magnets without using a rock saw and without demagnetizing the magnet obviously? Thanks in advance everyone.
  26. T

    Change temperature within very small timeframe

    I had no idea where to place this, so my apologies if I chose the wrong topic. Hi, For a certain application I need to heat very small (< 0.2 mm^3) quantities of ethanol until it vaporizes (78 °C) and then cool it down again until it's a liquid again. The hard part is that this all needs to...
  27. patrickmoloney

    Final Temperature of a monatomic gas

    Homework Statement The molar energy of a monatomic gas that obeys van der Waals' equation is given by E=\frac{3}{2}RT - \frac{a}{V} where V is the molar volume at temperature T and a is a constant. Initially, one mole of such a gas is at temperature T_1 and occupies a volume V_1. The gas is...
  28. D

    Show that Temperature remains unchanged in phase changes

    Well, I have to show mathematically that T remains unchanged in phase change. I know it comes from sperimental evidences, but my professor asked to show it with "numbers". So I thought to go like this: (dH_l)/dt ≈ (dm)/dt) h_v + Q Energy balance for system (let's say it is liquid and changes...
  29. S

    Temperature as a property of matter

    Can we consider temperature in general as "property" without even been associated to well defined states of matter. Like the boiling and melting points.
  30. D

    Fluid temperature change over cold surface?

    For my research I am trying to study the temperature change of a warm fluid (air) flowing over a cold surface, but I have not studied fluid mechanics. Does anyone know of an equation that can be used to analyze this problem? To give some reference, the hot air is 49 Celsius and the cold air is...
  31. runningman19

    Adiabatic Compressor: Ideal Gas Temperature Change

    Homework Statement A mixture of hydrogen, carbon monoxide and carbon dioxide is being fed to a compressor at 2.0 bar and 25 C. The overall flow rate is 17.47 SCMS and its composition is 73.5 mol% H2, 13.7 mol% CO and the balance CO2 The compressor operates adiabatically and reversibly with a...
  32. R

    Magnetic conductive material but thermally non conductive

    HI, I have application where i need to lift metal plate, 3kg weight, ( 3mmX 15mm), 250degree.C hot, for the period of 1min and put it back. For lifting purpose i am using actuators. As i have no opportunity to make hole in plate i have to use magnet for lifting purpose. I got Electromagnet...
  33. M

    MHB The Acidic Mysteries of Temperature and H2O

    why does the water become more acidic as temperature goes up. H2O <-> (H^+) + (OH^-) . why does this dissociate into the ions more at higher temperatures. also even if it does dissociate more it should not become more acidic as for every H^+ formed a OH^- is formed.
  34. L

    Resistance dependance on temperature for ohmic resistors

    Hello, I was giving a random thought to Ohm's Laws and thermal dilation. As a general rule we are told that ohmic resistors will increase their resistivity if their temperature increases. Does this take into account the fact that its dimensions will change due to thermal dilation? This would...
  35. F

    Binder cumulant g as a function of temperature

    Homework Statement Im doing a MC simulation with the ising model 2D. How can i calculate the Binder cumulant g as a function of temperature. To calculate the Binder cumulant, i will perform a scaling analysis f (finite scale scaling). Homework Equations U_L = 1 – { M^(4)_L / [ 3.(M^(2)_L)^2 ]...
  36. shihab-kol

    I-V graph of two wires and temperature

    Homework Statement Homework Equations ## V=IR## The Attempt at a Solution This is an I-V graph so the slope must represent ##\frac{1}{R} ## Now, $$ R∝Temperature$$ {This is assuming that the wires are of metal} Now , since the graph is of ##\frac{1}{R} ## , the steeper the slope the higher...
  37. 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?
  38. I

    What influences ignition temperature and oxygen consumption

    Hello, This is for my independent game development project. I am aiming to simulate simple environmental properties in grid-based world. I have world made of cells (or blocks) and I consider each physical property to be constant and uniform in given cell. Some properties spread from a cell to...
  39. S

    Magnetic Flux vs Temperature Relationship in Ferromagnets

    Hi everyone, I have recently done an experiment testing the effect of temperature on magnetism through measurement of magnetic flux at a constant distance away from the measuring device. I used a range of 0-90 C for neodymium and bar magnets, and found a reasonably linear trend, with a similar...
  40. E

    Internal energy of an ideal gas as a function of temperature

    Homework Statement Two containers hold an ideal gas at the same temperature and pressure. Both containers hold the same type of gas but container B has twice the volume of container A. The internal energy of the gas in container B is (a) twice that for container A (b) the same as that for...
  41. K

    Diamagnetic material's response to temperature change

    I know that in a para magnetic material the magnetization increase on cooling. What will be the same effect on a diamagnetic material,considering the fact that Curies law doesn't hold good on diamagnetic materials.
  42. L

    Problem with units for conduction rate?

    Homework Statement Consider the slab shown in Fig. 18-18. Suppose that L 25.0 cm, A 90.0 cm2, and the material is copper. If TH 125 C, TC 10.0 C, and a steady state is reached, find the conduction rate through the slab. Homework Equations Pcond = Kc *A*(TH - TC)/L K = 401 W/m*k The Attempt at...
  43. L

    How much water is converted to ice?

    Homework Statement A 0.530 kg sample of liquid water and a sample of ice are placed in a thermally insulated container. The container also contains a device that transfers energy as heat from the liquid water to the ice at a constant rate P, until thermal equilibrium is reached. The...
  44. Vivek98phyboy

    Gas Through Porous Plug: Pressure & Temp Change Explained

    I can't understand why a gas passing through a porous plug experiences change in its pressure and why does the cooling or heating process depends upon the initial temperature
  45. N

    Venus' temperature, radiation values and altitude

    Hi, I have a list of measured temperature values of Venus at altitudes from several missions to the planet. This temperature is a combination of outgoing thermal emission from the planet, incoming thermal emission from the sun and any chemical reactions going on in the atmosphere. Can I use...
  46. C

    Temperature prediction of a material

    I was not sure where to post this question so if anyone has a better home for it please advise. I am trying calculate how much temperature a given mass is required to be heated to (oven setting) to reach a target temperature on the surface of a metal like copper. I also need to know this...
  47. Anachronist

    Final pressure and temperature knowing only air mass outflow

    This seems simple, but I have some confusion. I'm trying to refine a numerical simulation to get away from my isothermal assumption, to account instead for isentropic temperature and pressure changes in pressure tank with an orifice. Given an insulating air tank of volume ##V##, containing air...
  48. N

    At what temperature does citric acid decay?

    I am currently performing a school experiment in which I am testing when citric acid decays. We are juicing lemons, filtering them to get a higher concentration of citric acid, placing them in water baths from 10 to 90 degrees Celsius and then titrating them against one mole of sodium hydroxide...
  49. D

    A Semiconductor temperature

    Hello I have got a question and i don't know the answer. Please help me. I have a n doped semiconductor. How does the number of conduction electrons depends on temperature and compare the situation to an intrinsic semiconductor? Do i look at the intrinsic density, because when it is n doped...
  50. K

    Speed of sound in steel dependance on temperature

    Hello, Nice easy question for you all today: I would like to know how the speed of sound in steel varies with temperature. A google search didnt reveal a great deal, so if a physicist could confirm the relationship, that would be much appreciated. I know that: v = √shear modulus/density...
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