Lambda point
Encyclopedia
The Lambda point is the temperature
(approximately 2.17 K
) below which normal fluid helium
(helium I) transitions to superfluid
helium II. More precisely, there is a lower lambda point at 2.172 K, 0.0497 atm
, and an upper one at 1.76 K, 29.8 atm.
The point's name derives from the graph that results from plotting the specific heat capacity as a function of temperature
(for a given pressure), which resembles the Greek
letter lambda
. The specific heat capacity tends towards infinity
as the temperature approaches the lambda point.
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
(approximately 2.17 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
) below which normal fluid helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
(helium I) transitions to superfluid
Superfluid
Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with extremely high thermal conductivity. The substance, which appears to be a normal liquid, will flow without friction past any surface, which allows it to continue to circulate over obstructions and...
helium II. More precisely, there is a lower lambda point at 2.172 K, 0.0497 atm
Atmosphere (unit)
The standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of pressure. For practical purposes it has been replaced by the bar which is 105 Pa...
, and an upper one at 1.76 K, 29.8 atm.
The point's name derives from the graph that results from plotting the specific heat capacity as a function of temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
(for a given pressure), which resembles the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
letter lambda
Lambda
Lambda is the 11th letter of the Greek alphabet. In the system of Greek numerals lambda has a value of 30. Lambda is related to the Phoenician letter Lamed . Letters in other alphabets that stemmed from lambda include the Roman L and the Cyrillic letter El...
. The specific heat capacity tends towards infinity
Infinity
Infinity is a concept in many fields, most predominantly mathematics and physics, that refers to a quantity without bound or end. People have developed various ideas throughout history about the nature of infinity...
as the temperature approaches the lambda point.
External links
- What is superfluidity? (includes a graph)