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Thermal physics

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Question 11
a.

Define the internal energy of an ideal gas.

[1]
b.

Use the formulae below to show that the average kinetic energy of a particle of an ideal gas is directly proportional to the absolute temperature of the gas.

pV=13Nmc2‾andpV=NkT pV = \frac{1}{3}N m \overline{c^2} \quad \text{and} \quad pV = NkT pV=31​Nmc2andpV=NkT
[3]
c.

The velocities of four gas particles at 290 K290\text{ K}290 K are given below in m s−1\text{m s}^{-1}m s−1:

290,360,410,520 290, \quad 360, \quad 410, \quad 520 290,360,410,520

Show that the root-mean-square (r.m.s.) speed of the sample is approximately 400 m s−1400\text{ m s}^{-1}400 m s−1.

[2]
d.

The velocities of four gas particles at 290 K290\text{ K}290 K are given below in m s−1\text{m s}^{-1}m s−1:

290,360,410,520 290, \quad 360, \quad 410, \quad 520 290,360,410,520

Calculate the molar mass of the gas assuming an absolute temperature of 290 K290\text{ K}290 K and an r.m.s. speed of 400 m s−1400\text{ m s}^{-1}400 m s−1.

[3]
e.

A sealed gas-filled ionization detector is manufactured by filling it with a noble gas at 290 K290\text{ K}290 K and low pressure.

When the detector is installed in an industrial monitoring system, it is exposed to constant thermal radiation and reaches a stable operating temperature of 980 K980\text{ K}980 K. At this temperature, the pressure inside the sealed detector is 220 kPa220\text{ kPa}220 kPa.

Explain, in terms of energy transfers, why the operating temperature of the detector remains constant at 980 K980\text{ K}980 K rather than continuing to rise. You are not expected to refer to the electrical properties of the detector.

[3]
f.

A sealed gas-filled ionization detector is manufactured by filling it with a noble gas at 290 K290\text{ K}290 K and low pressure.

When the detector is installed in an industrial monitoring system, it is exposed to constant thermal radiation and reaches a stable operating temperature of 980 K980\text{ K}980 K. At this temperature, the pressure inside the sealed detector is 220 kPa220\text{ kPa}220 kPa.

Calculate the pressure of the gas within the detector during manufacture (at 290 K290\text{ K}290 K).

[3]

Thermal physics Questions

  1. A Level
  2. /Physics
  3. /Thermal physics