Final answer:
When a brass ring is heated and slipped over an aluminum rod, both the ring and the rod will expand due to thermal expansion. The change in their diameters will depend on their coefficients of linear expansion and the temperature change.
Step-by-step explanation:
When the brass ring is heated, it expands due to thermal expansion. The same happens to the aluminum rod. Since the average coefficients of linear expansion are constant, we can assume that both the ring and the rod expand uniformly. The diameter of the ring increases, and when it is slipped over the rod, there will be a small gap between them. This is because the diameter of the rod is slightly larger than the initial diameter of the ring. The size of the gap and the final diameter of the ring and rod system will depend on their coefficients of linear expansion and the change in temperature.