A Ring and Ball - Chain (also known as a Captive Ring and Ball) is a variation of the thermal expansion apparatus where the ball is permanently attached to the ring handle by a short chain. This design ensures that the two matched pieces never become separated or lost in a busy lab environment.
Experimental Function
The core scientific principle remains the same as the two-piece set, but the chain allows for a specific variation called the "Expansion of a Hole" effect:
- Expansion of the Ball: When you heat the ball, it expands and becomes too large to pass through the cold ring.
- Expansion of the Ring: If you heat the ring instead of the ball, the diameter of the hole increases. This proves that when a hollow object is heated, it expands as if it were a solid piece of that material.
- Simultaneous Heating: If both the ball and ring are heated equally, the ball will still pass through, demonstrating that they are expanding at a proportional rate.
Design Features
- Captive Ball: The chain prevents the ball from being misplaced and allows it to hang safely while cooling.
- Matched Precision: The ball is machined to have a diameter just a fraction of a millimeter smaller than the inner diameter (ID) of the ring at room temperature.
- Safety Handles: Usually features a wooden or insulated plastic handle to protect the user while the brass components are held over a Bunsen burner.