critical temperature

(noun)

In superconducting materials, the characteristics of superconductivity appears at (and continues below) this temperature.

Related Terms

  • superconductivity
  • high-temperature superconductors

Examples of critical temperature in the following topics:

  • Temperature and Superconductivity

    • In superconducting materials, the characteristics of superconductivity appear when the temperature T is lowered below a critical temperature Tc.
    • The value of this critical temperature varies from material to material.
    • Solid mercury, for example, has a critical temperature of 4.2 K.
    • High-temperature superconductors can have much higher critical temperatures.
    • For example, YBa2Cu3O7, one of the first cuprate superconductors to be discovered, has a critical temperature of 92 K; mercury-based cuprates have been found with critical temperatures in excess of 130 K.
  • Dependence of Resistance on Temperature

    • Resistivity and resistance depend on temperature with the dependence being linear for small temperature changes and nonlinear for large.
    • The resistivity of all materials depends on temperature.
    • The temperature coefficient is typically +3×10−3 K−1 to +6×10−3 K−1 for metals near room temperature.
    • Above that critical temperature, its resistance makes a sudden jump and then increases nearly linearly with temperature.
    • Compare temperature dependence of resistivity and resistance for large and small temperature changes
  • Phase Changes and Energy Conservation

    • Temperature increases linearly with heat, until the melting point .
    • The curve ends at a point called the critical point, because at higher temperatures the liquid phase does not exist at any pressure.
    • The critical temperature for oxygen is -118ºC, so oxygen cannot be liquefied above this temperature.
    • Note that water changes states based on the pressure and temperature.
    • This graph shows the temperature of ice as heat is added.
  • Radiative Shocks

    • Astrophysically the rate that gas cools can depend very sensitively on the temperature of the gas.
    • Imagine if the gas before the shock was just below the critical temperature at which cooling set in.
    • As it passes through the shock, it goes above this temperature and then rapidly begins to cool and rapidly returns to its initial temperature.
    • The additional condition that we seek is that final temperature equals the initial temperature.
    • From the diagram it is apparent that the entropy of the gas decreases through an isothermal shock; as a gas is compressed at constant temperature, its entropy decreases.
  • Problems

    • the density at the critical radius is infinite, and the critical radius itself goes to zero.
    • Does most of the radiation emerge from regions at high temperature, at low temperatures or somewhere in between?
    • What and where is the peak temperature of the disk?
    • What and where is the minimum temperature of the disk?
    • You can use temperature units for the energy axis (i.e.
  • Absolute Temperature

    • Absolute temperature is the most commoly used thermodyanmic temperature unit and is the standard unit of temperature.
    • Thermodynamic temperature is the absolute measure of temperature.
    • Thermodynamic temperature is an "absolute" scale because it is the measure of the fundamental property underlying temperature: its null or zero point ("absolute zero") is the temperature at which the particle constituents of matter have minimal motion and cannot become any colder.
    • By using the absolute temperature scale (Kelvin system), which is the most commonly used thermodynamic temperature, we have shown that the average translational kinetic energy (KE) of a particle in a gas has a simple relationship to the temperature:
    • The kelvin (or "absolute temperature") is the standard thermodyanmic temperature unit.
  • Blackbody Temperatures

    • A blackbody is of course characterized by a single temperature, $T$.
    • There are three characteristic temperatures in common usage: brightness temperature, effective temperature and the colour temperature.
    • The brightness temperature is determined by equating the brightness or intensity of an astrophysical source to the intensity of a blackbody and solving for the temperature of the corresponding blackbody.
    • In what regime does the linear relationship between the brightness temperature and the intensity begin to fail?
    • Finally the effective temperature is the temperature of a blackbody that emits the same flux at its surface as the source, i.e.
  • Blackbody Radiation

    • A blackbody is of course characterized by a single temperature, $T$.
    • There are three characteristic temperatures in common usage: brightness temperature, effective temperature and the colour temperature.
    • The brightness temperature has several nice properties.
    • The colour temperature is defined by looking at the peak of the emission from the source and using Wien's displacement law to define a corresponding temperature.
    • Finally the effective temperature is the temperature of a blackbody that emits the same flux at its surface as the source, i.e.
  • Absolute Zero

    • Absolute zero is the coldest possible temperature; formally, it is the temperature at which entropy reaches its minimum value.
    • Absolute zerois the coldest possible temperature.
    • Formally, it is the temperature at which entropy reaches its minimum value.
    • Therefore, it is a natural choice as the null point for a temperature unit system.
    • A brief introduction to temperature and temperature scales for students studying thermal physics or thermodynamics.
  • Thermodynamics

    • A blackbody is of course characterized by a single temperature, $T$.
    • There are three characteristic temperatures in common usage: brightness temperature, effective temperature and the colour temperature.
    • The brightness temperature is determined by equating the brightness or intensity of an astrophysical source to the intensity of a blackbody and solving for the temperature of the corresponding blackbody.
    • In what regime does the linear relationship between the brightness temperature and the intensity begin to fail?
    • Finally the effective temperature is the temperature of a blackbody that emits the same flux at its surface as the source, i.e.
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