Define the internal energy of an ideal gas.
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=31Nmc2andpV=NkTThe velocities of four gas particles at 300 K300\text{ K}300 K are given below in m s−1\text{m s}^{-1}m s−1:
330,390,460,580 330, \quad 390, \quad 460, \quad 580 330,390,460,580Show that the root-mean-square (r.m.s.) speed of the sample is approximately 450 m s−1450\text{ m s}^{-1}450 m s−1.
Calculate the molar mass of the gas assuming an absolute temperature of 300 K300\text{ K}300 K and an r.m.s. speed of 450 m s−1450\text{ m s}^{-1}450 m s−1.
Halogen filament lamps are manufactured by a process where they are filled with a gas at 295 K295\text{ K}295 K and low pressure.
When the filament lamp is switched on, the filament reaches a constant temperature of 2800 K2800\text{ K}2800 K. At this temperature, the pressure inside the filament lamp is 160 kPa160\text{ kPa}160 kPa.
Explain, in terms of energy transfers, why the temperature of the filament does not increase beyond 2800 K2800\text{ K}2800 K. You are not expected to refer to the electrical characteristics of the filament lamp.
Calculate the pressure of the gas within the filament lamp during manufacture (at 295 K295\text{ K}295 K).
56 exam-style questions on OCR A A Level Physics Thermal physics, covering Temperature, Solid, liquid and gas, Thermal properties of materials, and Ideal gases. Each one has a worked solution and a mark scheme showing where the marks go.