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Welcome to our Physics lesson on Temperature and Energy, this is the first lesson of our suite of physics lessons covering the topic of Big Bang Model and Temperature, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
In Section 13, we provided the kinetic-molecular meaning of temperature. We have explained that the absolute temperature of a gas is related to the average kinetic energy of translational motion of all particles present in the (ideal) gas. If the gas is monoatomic, the kinetic energy of a single atom is given by
where k = 1.38 × 10-23 J/K is the Boltzmann constant. We assume that in the first stages of the Universe, particles have had a k ·T order of average kinetic energy. The coefficient before k · T depends on the number of gas atoms in the molecules involved (3/2 for monoatomic, 5/2 for diatomic and 3 for polyatomic gases).
When particles of a gas collide with each other, they exchange energy. The energy exchanged between colliding particles is of the same order as the value of their average kinetic energy. Hence, we have
Since the energy exchanged for 1 particle is very small, it is often expressed in GeV (giga electronvolt). Giving that 1eV = 1.6 × 10-19 J, express the Boltzmann constant in GeV/K.
All what we have to do is to divide the value of Boltzmann constant expressed in J/K by the conversion factor between joule and electronvolt. We have
Since 1 giga = 109, we have for the value of k expressed in GeV/K:
In high temperatures, the energy exchanged during collisions is very high. As a result, in different temperatures there are different types of interactions between particles in the universe.
You have reached the end of Physics lesson 22.10.1 Temperature and Energy. There are 6 lessons in this physics tutorial covering Big Bang Model and Temperature, you can access all the lessons from this tutorial below.
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