Kinetic Theory & Ideal Gases — Multiple-Choice Questions (Edexcel IAL Physics): Exam Questions

A fixed mass of an ideal gas has a volume V and exerts a pressure p. The absolute temperature of the gas is T. When the gas is heated, the new pressure is 4p.

Which row of the table gives correct values of the new volume and the new temperature?

Helium gas in a closed cylinder is heated until the pressure exerted by the helium is four times the original pressure. The volume occupied by the helium stays constant.

The mean square speed of the helium molecules before heating is $\langle v_{1}^{2} \rangle$. The mean square speed of the helium molecules after heating is $\langle v_{F}^{2} \rangle$.

What is the ratio $\langle \frac{v_{F}^{2} }{v_{1}^{2} } \rangle$?

Which of the following graphs shows how the internal energy $U$ of an ideal gas varies with the absolute temperature $T$ of the gas?

The solar corona is the outermost layer of the Sun's atmosphere. It consists of a highly ionised gas called a plasma, and is composed mostly of protons and electrons.

In a particular region of the corona, the temperature is $2.0\times10^{6}\text{K}$ and the number density of particles is about $1.1\times10^{15}\text{m}^{-3}$.

A plasma can be considered to behave as an ideal gas when the mean thermal kinetic energy of the particles is much greater than the average electric potential energy between them.

Deduce whether the plasma in the solar corona behaves as an ideal gas.