Question

$ABCDEFGH$ is a hollow cube made of an insulator (Figure). Face $ABCD$ has positive charge on it. Inside the cube, we have ionized hydrogen. The usual kinetic theory expression for pressure

• A. will not be valid because isotropy is lost.
• B. will be valid.
• C. will not be valid since the ions would experience forces other than due to collisions with the walls.
• D. will not be valid since collisions with walls would not be elastic.

Answer 1

Answer: (A), (C)

will not be valid since the ions would experience forces other than due to collisions with the walls.

As ions of hydrogen are present inside the cube, they are having charge. Now, due to presence of positive charge on the surface $ABCD$, hydrogen ions would experience forces of electrostatic nature. The usual expression for pressure based on kinetic theory will not be valid as ions would also experience electrostatic forces other than the forces due to collisions with the walls of the container.

Due to presence of positive charge, the isotropy is also lost.

$\text{Final Answer}:$ (b), (d).