A ‘s Gravesande’s ring is an apparatus for demonstrating thermal expansion and contraction, a fundamental principle in thermodynamics. Named after Dutch scientist Willem ‘s Gravesande, the apparatus consists of two main components: a brass ring, and a brass ball slightly smaller in diameter than the ring.
The ball can pass freely through the ring when both are at the same temperature. However, when the ball is heated, it undergoes thermal expansion and no longer fits through the ring. Once it cools down, it contracts and is again able to pass through. At a microscopic level, when the brass ball is heated, the kinetic energy of its molecules increases.