About the thermodynamic property Temperature disambiguation File Annual Average Temperature Map.jpg thumb 400px Annual mean temperature around the world Temperature is a physical property of matter that quantitatively expresses the common notions of heat hot and cold . Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot. Quantitatively, temperature is measured with thermometers , which may be calibration calibrated to a variety of Temperature conversion formulas temperature scales . Much of the world uses the Celsius scale C for most temperature measurements. It has the same incremental scaling as the Kelvin scale used by scientists ... Historically, the Celsius scale was a purely empirical temperature scale defined only by the freezing ... temperature measurement, the International System of Units SI defines a scale and unit for the thermodynamic temperature by using the easily reproducible temperature of the triple point of water ... first defined the scale. The unit symbol of the kelvin is K. Temperature is one of the principal ... in temperature between regions of matter, because such differences are the driving force for heat ... Consequently we identify temperature as a driving force which causes something called heat to be transferred ... of higher temperature to regions of lower temperature. If no heat is transferred between two objects, the objects have the same temperature. In the classical thermodynamic approach to temperature, temperature of an object varies with the speed of the particles it contains, raised to the second power. Therefore, temperature is tied directly to the mean kinetic energy of particles moving relative to the center of mass coordinates for that object. Temperature is an Intensive and extensive properties ... inside, be they atoms, molecules, or electrons. In order for the temperature of a system to be defined, the system must be in thermodynamic equilibrium . Temperature may be considered to vary with position ... more details
Temperature range may refer to Atmospheric temperature An aspect of Climate Climate classification climate classification Diurnal temperature variation Operating temperatureTemperature Thermoregulation Disambiguation ... more details
wiktionarypar temperatureTemperature is a physical property of a system that underlies the common notions of hot and cold. Closely related are Thermodynamic temperature Color temperature Effective temperature Normal human body temperature The term may also refer to Noise temperature , a measure of the noise of an electronic component. Temperature meat , or doneness, a description of how thoroughly cooked a cut of meat is Temperature song Temperature song , a song by Sean Paul Temperature Zion I song Temperature Zion I song Temperature , a song by Blaque from Blaque Out Temperature , a song by Little Walter Albums Little Walter See also Lookfrom Temperature disambig ca Temperatura desambiguaci de Temperatur Begriffskl rung la Temperatura discretiva lt Temperat ra reik m s pl Temperatura ujednoznacznienie ... more details
wiktionarypar melting temperature Melting temperature may refer to Melting point , the temperature at which a substance changes from solid to liquid state. Tm 81.5 0.41 GC pair 675 N N mer number of nucleotides DNA melting temperature , the temperature at which a DNA double helix dissociates into single strands. disambig ... more details
Unreferenced date February 2008 Transition temperature is the temperature at which a material changes from one crystal state Allotropy allotrope to another. There are seven crystal system s and every material exists in one of them. In the case of ferroelectric or ferromagnetic crystals a transition temperature may be known as the Curie temperature . Transition temperature is the temperature at which a solid changes state, either becoming softer when heated or more brittle when cooled. Transition temperature is the temperature above and below which solubility changes in a noticibly different way. On a graph the transition temperature is deduced by the intersection of two lines each of which have a different gradient. Category Crystallography Chemistry stub ... more details
Refimprove date April 2009 Orphan date February 2009 The permissive temperature is the temperature at which a temperature sensitive mutant gene product takes on a normal, functional phenotype. ref http www.biology online.org dictionary Permissive temperature ref When a temperature sensitive mutant is grown in a permissive condition, the mutant mutated gene product behaves normally meaning that the phenotype isn t observed , even if there is a mutant allele present. This results in the survival of the cell or organism, as if it were a wild type strain. In contrast, the nonpermissive temperature or restrictive temperature is the temperature at which the mutant phenotype is observed. Most temperature sensitive mutations affect proteins, and are recessive and cause loss of protein function at the non permissive temperature. The permissive temperature is one at which the protein typically can fold properly, or remain properly folded. References Reflist Category Temperature Category Cell biology Category Biology terminology biochemistry stub ... more details
Apparent temperature is the general term for the perceived outdoor temperature, caused by the combined effects of air temperature , relative humidity and wind speed . The Heat index measures the effect of humidity on the perception of temperature. In humid conditions, the air feels hotter than it actually is, because of the reduction of perspiration . The Wind chill measures the effect of wind speed on the perception of temperature. In windy conditions, the air feels cooler than it actually is, because of increased perspiration. The Wet Bulb Globe Temperature WBGT combines the effects of radiation, humidity, temperature and wind speed on the perception of temperature. It is not often used as the resulting figure is very location specific eg cloud cover and or wind shielding . Disambig ... more details
Temperature cycling or temperature cycle is the process of cycling through two temperature extremes, typically at relatively high rates of change. It is an environmental Stress testing stress test used in evaluating product Reliability engineering reliability as well as in manufacturing to catch early term, latent defects by inducing failure through thermal Fatigue material fatigue . External links http www.motorola.com testservices temperature1.html Temperature Testing Motorola http www.jedec.org download search 22a104d.pdf Temperature Cycling JEDEC Standard No. 22 A104D http www.siliconfareast.com TCT.htm Temperature Cycle Test SiliconFarEast.com http www.siliconfareast.com faq tc life.htm Equivalent Life of Temperature Cycle Testing SiliconFarEast.com Category Reliability engineering ... more details
Temperature Rising may refer to Temperature Rising album , a studio album by Thai singer Tata Young Temperatures Rising , an American television situation comedy Temperature s Rising , an album by rock group Loverboy Temperature s Rising Mobb Deep song Temperature s Rising Mobb Deep song a single by Mobb Deep off of the 1995 album The Infamous disambig ... more details
Junction temperature is the highest temperature of the actual semiconductor in an electronic device. In operation it is higher than case temperature and the temperature of the part s exterior. The difference is equal to the amount of heat transferred from the junction to case multiplied by the junction to case thermal resistance . Maximum junction temperature is specified in a part s datasheet and is used when calculating the necessary case to ambient thermal resistance for a given power dissipation. This in turn is used to select an appropriate heat sink if necessary. An estimation of the chip junction temperature, T sub J sub , can be obtained from the following equation T sub J sub T sub A sub R sub JA sub P sub D sub where T sub A sub ambient temperature for the package C R sub JA sub junction to ambient thermal resistance C W P sub D sub power dissipation in package W DEFAULTSORT Junction temperature Category Semiconductors physics stub zh ... more details
38.7.JPG thumb right A medical clinical thermometer showing the temperature of 38.7 C Attempts of standardized temperature measurement have been reported as early as 170 AD by Galen Claudius Galenus . ref name quinn cite book author T. J. Quinn year 1983 title Temperature publisher Academic Press ... in the 17th century. Early devices to measure temperature were called thermoscope s. The first ... The development of today s thermometer s and temperature scales began in the early 18th century, when ... and the Kelvin scale. Technologies Many methods have been developed for measuring temperature. Most of these rely on measuring some physical property of a working material that varies with temperature. One of the most common devices for measuring temperature is the mercury in glass thermometer glass ..., which acts as the working fluid. Temperature increases cause the fluid to expand, so the temperature ... so that one can read the temperature simply by observing the level of the fluid in the thermometer ... standpoint, is the gas thermometer . Other important devices for measuring temperature include Thermocouple s Thermistor s Resistance Temperature Detector RTD Pyrometer Langmuir probe s for electron temperature of a Plasma physics plasma Infrared Other thermometer s One must be careful when measuring temperature to ensure that the measuring instrument thermometer, thermocouple, etc. is really the same temperature as the material that is being measured. Under some conditions heat from the measuring instrument can cause a temperature gradient, so the measured temperature is different from the actual temperature of the system. In such a case the measured temperature will vary not only with the temperature of the system, but also with the heat transfer properties of the system. An extreme ... windy conditions than calm conditions even though the temperature is the same. What is happening is that the wind ... temperature for the same ambient temperature. The theoretical basis for thermometers is the zeroth ... more details
Refimprove date June 2009 Room temperature is a common term that can either denote a certain temperature to which humans are accustomed or a specific temperature. In the United Kingdom for instance, room temperature is traditionally 18 Celsius C 64 Fahrenheit F Fact date January 2011 but is now regarded as being too cool, possibly due to the widespread use of central heating Fact date January 2011 reason this seems to be a contradiction of the first part of this sentence . Room temperature may otherwise ... 2011 The term can also refer to a temperature of food to be consumed, which is placed in such a room ..., room temperature is usually taken to be either 20 or 25 degrees Celsius 293 or 298 kelvin ... F is often used, without being specified as room temperature . Fact date June 2009 However, room temperature is not a uniformly defined scientific term, unlike Standard conditions for temperature and pressure Standard Temperature and Pressure , or STP, which has several, slightly different definitions. Ambient versus room temperature Room temperature implies a temperature inside a temperature controlled building. Ambient temperature simply means the temperature of the surroundings and will be the same as room temperature indoors. In many languages, such as Spanish, there is an expression for ambient temperature , but no distinct translation for room temperature . Wine serving temperature Red wine is often quoted as one that is best served at room temperature . This is not quite true nowadays. In modern, heated or air conditioned buildings, a comfortable temperature is usually higher ... temperature for longer. Detailed recommendations about optimal serving temperature for each ... air Standard conditions for temperature and pressure Standard temperature and pressure STP References Reflist Category Heat transfer Category Science experiments Category Temperature af Kamertemperatuur ... simple Room temperature sv Rumstemperatur ta th ur ... more details
The temperature coefficient is the relative change of a physical property when the temperature is changed by 1 Kelvin K . In the following formula, let R be the physical property to be measured and T be the temperature at which the property is measured. T sub 0 sub is the reference temperature, and T is the difference between T and T sub 0 sub . Finally, is the linear temperature coefficient ... Delta T math Here has the dimension s of an inverse temperature 1 K or K sup 1 sup . This equation is linear with respect to temperature. For quantities that vary polynomial ly or logarithm ically with temperature, it may be possible to calculate a temperature coefficient that is a useful approximation ... with temperature, such as Arrhenius equation the rate of a chemical reaction , any temperature coefficient would be valid only over a very small temperature range. Different temperature coefficients are specified for various applications, including nuclear, electrical and magnetic. Negative temperature coefficient A negative temperature coefficient NTC occurs when the thermal conductivity of a material rises with increasing temperature, typically in a defined temperature range. For most materials, the thermal conductivity will decrease with increasing temperature. Materials with a negative temperature coefficient have been used in floor heating since 1971. The negative temperature coefficient ... frac B T math where R is resistance, A and B are constants, and T is absolute temperature K . The constant ... sensitivity to temperature. Such is the importance of the B constant value, that it is possible to characterize ... T 0 e frac B T math where math R 0 math is resistance at temperature math T 0 math . Therefore, many ... for the electrical conduction from these defect centers. Reversible temperature coefficient Residual magnetic flux density or Magnetic field B and H Br changes with temperature and it is one of the important ... wave tube s TWTs , need to have constant field over a wide temperature range . The reversible ... more details
The vibrational temperature is commonly used in thermodynamics , to simplify certain equations. It has units of temperature and is defined as math theta vib frac hc nu k B math br where math k B math is Boltzmann s constant The vibrational temperature is used commonly when finding the vibrational partition function . References http www.chem.arizona.edu salzmanr 480b statt02 statt02.html Statistical thermodynamics University Arizona See also Rotational temperature Rotational spectroscopy Vibrational spectroscopy Infrared spectroscopy Spectroscopy Category Atomic physics Category Molecular physics ... more details
Unreferenced date November 2006 The Excitation Temperature math T ex math often called the spin temperature for the 21 cm line is defined for a population of particles via the Boltzmann factor . It satisfies math frac n u n l frac g u g l exp frac Delta E k T ex , math where n sub u sub and n sub l sub represent the number of particles in an upper e.g. excited and lower e.g. ground state, and g sub u sub and g sub l sub their statistical weights respectively. Thus the excitation temperature is the temperature at which we would expect to find a system with this ratio of level populations. However it has no actual physical meaning except when in local thermodynamical equilibrium. The excitation temperature can even be negative for a system with inverted levels such as a maser . DEFAULTSORT Excitation Temperature Category Temperature Category Physics ... more details
In fluid dynamics , the film temperature T sub f sub , sometimes called the surface temperature , is the temperature of a fluid at the inside surface of a heater . For fired heaters, T sub f sub is usually measured inside the tube at the wall, but for electric immersion heaters, it is measured at the surface of the heating element . The film temperature is the arithmetic mean of the wall temperature T sub W sub and the free stream temperature T sub sub . Mathematically, this can be expressed as math T text f frac T text W T mathrm infty 2 math External links http www.paratherm.com tipsheets tipsheet fluid life film temperature.asp Film Temperature http www.multitherm.com technical articles bulk film temp impact.html Bulk and Film Temperatures Category Fluid dynamics physics stub it Temperatura di film pt Temperatura de pel cula ... more details
In fluid dynamics , the bulk temperature , or the average fluid bulk temperature , is a convenient reference point for evaluating properties related to convective heat transfer , particularly in applications related to flow in pipe material pipes and duct HVAC ducts . The concept of the bulk temperature is that adiabatic mixing of the fluid from a given cross section of the duct will result in some equilibrium temperature that accurately reflects the average temperature of the moving fluid, more so than a simple average like the film temperature . ref Kreith, Frank, and Bohn, Mark S. Principles of Heat Transfer, Sixth Edition. Brooks Cole Pacific Grove, CA, 2001. ref References references Category Fluid dynamics Category Thermodynamics Category Heat transfer fluiddynamics stub ... more details
For temperature control in organisms Thermoregulation Unreferenced date August 2009 Temperature control is a process in which change of temperature of a space and objects collectively therewithin is measured or otherwise detected, and the passage of heat energy into or out of the space is adjusted to achieve a desired average temperature. Control loops A home thermostat is an example of a closed control loop It constantly assesses the current room temperature and controls a heater and or air conditioner to increase or decrease the temperature according to user defined setting s . A simple low cost, cheap thermostat merely switches the heater or air conditioner either on or off, and temporary overshoot and undershoot of the desired average temperature must be expected. A more expensive thermostat varies the amount of heat or cooling provided by the heater or cooler, depending on the difference between the required temperature the setpoint and the actual temperature. This minimizes over undershoot. The process is called PID and is implemented using a PID controller PID Controller . Energy balance An object s or space s temperature increases when heat energy moves into it, increasing the average kinetic energy of its atoms, e.g., of things and air in a room. Heat energy leaving an object or space lowers its temperature. Heat flows from one place to another always from a higher temperature to a lower one by one or more of three processes heat conduction conduction , convection and radiation . In conduction, energy is passed from one atom to another by direct contact. In convection ... or thing, more energy is received than is lost, its temperature increases. If the amount of energy coming in and going out are exactly the same, the temperature stays constant there is thermal ... bed heat exchanger Thermodynamic equilibrium External links http www.hbtem.com Global Temperature Controller DEFAULTSORT Temperature Control Category Temperature control ... more details
The Krafft temperature also known as Krafft point , or critical micelle temperature is the minimum temperature at which surfactant s form micelle s. Below the Krafft temperature, there is no value for the critical micelle concentration CMC , i.e., micelles cannot form. The Krafft temperature is a point of phase change below which the surfactant remains in crystalline form, even in aqueous solution. Surfactants in such a crystalline state will only solubilize and form micelles if another surfactant assists it in overcoming the forces that keep it crystallized, or if the temperature increases, thus causing entropy to have a stronger force and encouraging the crystalline structure to break apart. Structural Effects Surfactants are usually composed of a hydrocarbon chain and a polar head group. Increasing the length of the hydrocarbon chain increases the Krafft temperature because it improves Van der Waals force Van der Waals forces. External links http goldbook.iupac.org K03415.html IUPAC Gold book Krafft temperature chem stub Category Colloidal chemistry Category Physical chemistry de Krafft Punkt it Temperatura di Krafft nl Krafft temperatuur ja ... more details
Unreferenced stub auto yes date December 2009 If the velocity velocities of a group of electron s, e.g., in a plasma physics plasma , follow a Maxwell Boltzmann distribution Distribution of the velocity vector Maxwell Boltzmann distribution , then the electron temperature is well defined as the temperature of that distribution. For other distributions, two thirds of the average energy is often referred to as the temperature, since for a Maxwell Boltzmann distribution with three Degrees of freedom physics and chemistry degrees of freedom , math langle E rangle 3 2 langle k BT rangle math . The International System of Units SI unit of temperature is the kelvin K , but using the above relation the electron temperature is often expressed in terms of the energy unit electronvolt eV . 1 K corresponds to 8.617343 15 10 sup 5 sup eV this factor is the ratio of the Boltzmann constant to the elementary charge . The electron temperature of a plasma can be several orders of magnitude higher than the temperature of the neutral species or of the ion s. This is a result of two facts. Firstly, many plasma source s heat the electrons more strongly than the ions. Secondly, atoms and ions are much heavier than electrons, and energy transfer in a two body collision is much more efficient if the masses are similar. DEFAULTSORT Electron Temperature Categories Category Plasma physics Physics stub sv Elektrontemperatur ... more details
Annealing temperature may refer to Annealing glass Annealing metallurgy Polymerase chain reaction dab Long comment to avoid being listed on short pages ... more details
Refimprove date December 2009 Operative temperature math t o math is defined as a uniform temperature of a radiantly black enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual nonuniform environment. ref ASHRAE Terminology, ASHRAE Handbook CD, 1999 2002 ref Some references also use the terms equivalent temperature or effective temperature to describe combined effects of convective and radiant heat transfer. ref Nilsson, H.O., Comfort Climate Evaluation with Thermal Manikin Methods and Computer Simulation Models, National Institute for Working Life, 2004, pg. 37 ref In design, operative temperature can be defined as the average of the Mean radiant temperature mean radiant and Dry bulb temperature ambient air temperatures , weighted by their respective heat transfer coefficient s. ref Thermal Comfort, ASHRAE Handbook, Fundamentals, Ch. 9, pg.3, 2009 ref The instrument used for assessing environmental thermal comfort in terms of operative temperature is called a eupatheoscope and was invented by A. F. Dufton in 1929. ref Glossary of Meteorology, American Meteorological Society, http amsglossary.allenpress.com glossary browse?s e&p 42 , accessed Sept 2010 ref Mathematically, operative temperature can be shown as big math t o frac h r t mr h c t a h r h c math big where, math h c math convective heat transfer coefficient math h r math linear radiative heat transfer coefficient math t a math air temperature math t mr math mean radiant temperature Application Operative temperature is used in heat transfer and thermal comfort analysis in transportation and buildings. ref Dufton, A. F. The Equivalent Temperature of a room ... psychrometric charts used in HVAC design only show the dry bulb temperature on the x axis abscissa , however, it is the operative temperature which is specified on the x axis of the psychrometric chart ... also HVAC Psychrometrics Underfloor heating ASHRAE References Reflist DEFAULTSORT Operative Temperature ... more details
About radiometric dating blocking temperature in a ferromagnet Superparamagnetism In radiometric dating , closure temperature or blocking temperature refers to the temperature of a system, such as a mineral , at the time given by its radiometric date. In physical terms, the closure temperature at which a system has cooled so that there is no longer any exchange of parent or daughter isotopes with the external environment. This temperature varies broadly between different minerals and also differs depending on the parent and daughter atoms being considered. ref Earth a Portrait of a Planet http www.wwnorton.com college geo earth2 glossary b.htm Glossary W.W. Norton & Company ref It is specific to a particular material and isotopic system. ref name Rollinson Rollinson, 1993. Using Geochemical Data Evaluation, Presentation, Interpretation Longman Scientific & Technical. ISBN 978 0 582 06701 1 ref These temperatures are experimentally determined in the lab by Petrology Branches artificially resetting sample mineral s using a high temperature furnace. As the mineral cools, the crystal structure begins to form and diffusion of isotope s is less easy. At a certain temperature, the crystal structure has formed sufficiently to prevent diffusion of isotopes. This temperature is what is known as blocking temperature and represents the temperature below which the mineral is a closed system to isotopes. ref name Rollinson Thus an igneous or metamorphic rock or melt, which is slowly cooling, does not begin to exhibit measurable radioactive decay until it cools below the blocking temperature ... cooled to blocking temperature. These temperatures can also be determined in the field by comparing ... values of the closure temperature require more precise calculations and characterizations of the diffusion ... 1 Mineral Closure temperature C Hornblende 530 40 Muscovite 350 Biotite 280 40 Uranium lead method class wikitable border 1 Mineral Closure temperature C ref cite journal doi 10.1130 G21010.1 title ... more details
The convective temperature CT or T sub c sub is the approximate temperature that air near the surface must reach for cloud formation without mechanical lift. In such case, cloud base begins at the convective condensation level CCL , whilst with mechanical lifting, condensation begins at the lifted condensation level LCL . Convective temperature is important to forecasting thunderstorm development. See also Atmospheric thermodynamics Meteorological variables climate stub Category Severe weather and convection Category Atmospheric thermodynamics ja ... more details
Multiple issues wikify January 2011 dead end January 2011 orphan January 2011 unreferenced January 2011 Temperature strips are flexible, often disposable visual indicators used to quickly and easily take and monitor surface temperature. They are used in laboratory, food and beverage, hospital and home applications, and often use a gradient color scheme to communicate a safe or out of tolerance condition. DEFAULTSORT Temperature Strip Category Thermometers ... more details
Encyclopedia
top
