As Column A gets heated, the balI moves left along the beam. The solid ball cannot fit through the ring because it grows larger and expands when heated.
Heat causes a substance's molecules and atoms to vibrate more quickly. Atoms that vibrate more swiftly separate themselves from one another. The state of matter of a substance is determined by the velocity and spacing of the particles. The thing finally grows and takes up more space as a result of increased molecular mobility. Heat causes the molecules in the thermometer's red liquid to flow more swiftly. This movement causes the molecules to spread out a little bit further, which competes with their mutual attractions. They can only get out by climbing the tube.