ized by j-j coupling. The multiplets of
many atoms and nuclei are intermediate between j-j coupling and *Russell–Saunders coupling, a state called
intermediate coupling.
Joliot-Curie, Irène (1897–1956)
French physicist, daughter of Marie
and Pierre *Curie, who was educated
by her mother and her scientist associates. In 1921 she began work at the
Radium Institute, becoming director
in 1946. In 1926 she married Frédéric
Joliot (1900–58). They shared the
1935 Nobel Prize for chemistry for
their discovery of artiÜcial radioactivity the previous year.
joliotium See transactinide elements.
JMol A commonly used molecular
viewing program similar to RasMol.
It can be used as an applet in a web
page.
A
• Details and a download for JMol from
SourceForge
joule Symbol J. The *SI unit of
work and energy equal to the work
done when the point of application
of a force of one newton moves, in
the direction of the force, a distance
of one metre. 1 joule = 10
7 ergs =
0.2388 calorie. It is named after
James Prescott *Joule.
Joule, James Prescott (1818–89)
British physicist. In 1840 he discovered the relationship between electric current passing through a wire,
its resistance, and the amount of
heat produced. In 1849 he gave an account of the kinetic theory of gases,
and a year later announced his bestknown Ünding, the mechanical
equivalent of heat. Later, with
William Thomson (Lord *Kelvin), he
discovered the *Joule–Thomson effect.
Joule’s law The *internal energy
of a given mass of gas is independent
of its volume and pressure, being a
function of temperature alone. This
law, which was formulated by James
Prescott Joule, applies only to *ideal
gases (for which it provides a deÜnition of thermodynamic temperature)
as in a real gas intermolecular forces
would cause changes in the internal
energy should a change of volume
occur. See also joule–thomson
effect.
Joule–Thomson effect (Joule–
Kelvin effect) The change in temperature that occurs when a gas expands
through a porous plug into a region
of lower pressure. For most real gases
the temperature falls under these circumstances as the gas has to do internal work in overcoming the
intermolecular forces to enable the
expansion to take place. This is a deviation from *Joule’s law. There is
usually also a deviation from *Boyle’s
law, which can cause either a rise or
a fall in temperature since any increase in the product of pressure and
volume is a measure of external
work done. At a given pressure, there
is a particular temperature, called
the inversion temperature of the gas,
at which the rise in temperature
from the Boyle’s law deviation is balanced by the fall from the Joule’s law
deviation. There is then no temperature change. Above the inversion
temperature the gas is heated by expansion, below it, it is cooled. The effect was discovered by James Prescott
Joule working in collaboration with
William Thomson (later Lord Kelvin).
301
Joule–Thomson effect
j
www.AzShimi.ir www.AzShimi.com
many atoms and nuclei are intermediate between j-j coupling and *Russell–Saunders coupling, a state called
intermediate coupling.
Joliot-Curie, Irène (1897–1956)
French physicist, daughter of Marie
and Pierre *Curie, who was educated
by her mother and her scientist associates. In 1921 she began work at the
Radium Institute, becoming director
in 1946. In 1926 she married Frédéric
Joliot (1900–58). They shared the
1935 Nobel Prize for chemistry for
their discovery of artiÜcial radioactivity the previous year.
joliotium See transactinide elements.
JMol A commonly used molecular
viewing program similar to RasMol.
It can be used as an applet in a web
page.
A
• Details and a download for JMol from
SourceForge
joule Symbol J. The *SI unit of
work and energy equal to the work
done when the point of application
of a force of one newton moves, in
the direction of the force, a distance
of one metre. 1 joule = 10
7 ergs =
0.2388 calorie. It is named after
James Prescott *Joule.
Joule, James Prescott (1818–89)
British physicist. In 1840 he discovered the relationship between electric current passing through a wire,
its resistance, and the amount of
heat produced. In 1849 he gave an account of the kinetic theory of gases,
and a year later announced his bestknown Ünding, the mechanical
equivalent of heat. Later, with
William Thomson (Lord *Kelvin), he
discovered the *Joule–Thomson effect.
Joule’s law The *internal energy
of a given mass of gas is independent
of its volume and pressure, being a
function of temperature alone. This
law, which was formulated by James
Prescott Joule, applies only to *ideal
gases (for which it provides a deÜnition of thermodynamic temperature)
as in a real gas intermolecular forces
would cause changes in the internal
energy should a change of volume
occur. See also joule–thomson
effect.
Joule–Thomson effect (Joule–
Kelvin effect) The change in temperature that occurs when a gas expands
through a porous plug into a region
of lower pressure. For most real gases
the temperature falls under these circumstances as the gas has to do internal work in overcoming the
intermolecular forces to enable the
expansion to take place. This is a deviation from *Joule’s law. There is
usually also a deviation from *Boyle’s
law, which can cause either a rise or
a fall in temperature since any increase in the product of pressure and
volume is a measure of external
work done. At a given pressure, there
is a particular temperature, called
the inversion temperature of the gas,
at which the rise in temperature
from the Boyle’s law deviation is balanced by the fall from the Joule’s law
deviation. There is then no temperature change. Above the inversion
temperature the gas is heated by expansion, below it, it is cooled. The effect was discovered by James Prescott
Joule working in collaboration with
William Thomson (later Lord Kelvin).
301
Joule–Thomson effect
j
www.AzShimi.ir www.AzShimi.com