A brass disc fits snugly in a hole in a steel plate. Should you heat or cool this system to losen the disc from the hole ? given that `alpha _b gt alpha _Fe`.

Explanation

To determine whether to heat or cool a system consisting of a brass disc snugly fitting in a hole in a steel plate, we need to consider the coefficients of linear expansion for both materials.

### Step-by-Step Solution:

1. **Understand the Coefficients of Linear Expansion**:
- The coefficient of linear expansion (α) indicates how much a material expands or contracts per degree change in temperature.
- In this case, we are given that the coefficient of linear expansion for brass (α_b) is greater than that for steel (α_Fe).

2. **Analyze the Effect of Temperature Change**:
- When the temperature of a material increases, it expands. Conversely, when the temperature decreases, it contracts.
- Since α_b > α_Fe, this means that brass will expand more than steel when heated and contract more than steel when cooled.

3. **Determine the Action to Take**:
- To loosen the brass disc from the steel plate, we want the disc to become smaller relative to the hole in the plate.
- If we **cool** the system, the brass disc will contract more than the steel plate due to its higher coefficient of linear expansion. This will create more space for the disc, allowing it to loosen from the hole.

4. **Conclusion**:
- Therefore, to loosen the brass disc from the hole in the steel plate, we should **cool the system**.

### Final Answer:
We should cool the system to loosen the disc from the hole.

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