Class 11 Physics Kinetic Theory Kinetic Interpretation of Temperature

Kinetic Interpretation of Temperature

Molecules going through a porous wall

Problem:-

Estimate the average thermal energy of a helium atom at (i) room temperature (27 °C),

(ii) The temperature on the surface of the Sun (6000 K), (iii) the temperature of 10 millionKelvin (the typical core temperature in the case of a star).

At room temperature, T = 27°C = 300 K

Average thermal energy= (3/2) kT

Where k is Boltzmann constant = 1.38 × 10–23 m2 kg s–2 K–1

(3/2) kT= (3/2) x1.38x10-38x300= 6.21 × 10–21J

Hence, the average thermal energy of a helium atom at room temperature (27°C) is

=6.21× 10–21 J.

On the surface of the sun, T = 6000 K

Average thermal energy= (3/2) kT

= (3/2) x1.38x10-38x6000

= 1.241 × 10–19 J

Hence, the average thermal energy of a helium atom on the surface of the sun is

=1.241 ×10–19 J.

At temperature, T = 107 K

Average thermal energy= (3/2) kT

= (3/2) x1.38x10-23x107

= 2.07 × 10–16 J

Hence, the average thermal energy of a helium atom at the core of a star is 2.07 ×10–16

.