A circular part is cutted from a rectangular plate. Then the cutted plate is heated constantly. What will be the effect of heat on the circular hole?

(a). the size of hole will increase.

(b). the size of hole will decrease.

When a circular part is cut from a rectangular plate and the remaining plate is heated, the effect of heat on the circular hole is quite interesting. The correct answer is (a) the size of the hole will increase. Let’s delve into the reasoning behind this phenomenon.

Understanding Thermal Expansion

To grasp why the hole expands when heated, we need to consider the concept of thermal expansion. Most materials, including metals and plastics, expand when they are heated. This expansion occurs because the atoms within the material gain energy and move more vigorously, causing them to take up more space.

Behavior of the Plate and the Hole

When the rectangular plate is heated, the entire material—including the area surrounding the circular hole—expands. However, the hole itself does not contain any material; it is simply an absence of material. As the surrounding material expands, it pushes outward, effectively increasing the diameter of the hole.

Visualizing the Expansion

Imagine a rubber band. If you stretch it, the space in the middle becomes larger. Similarly, when the plate heats up, the edges of the hole are like the rubber band being pulled apart. The material around the hole expands outward, leading to an increase in the size of the hole.

Real-World Examples

• Bridges: Engineers account for thermal expansion in bridge design. Gaps are left between sections to allow for expansion during hot weather.
• Metal Rings: If you heat a metal ring, it will expand, making the hole in the center larger. This principle is often used in manufacturing to fit parts together.

Factors Influencing Expansion

The extent to which the hole expands depends on several factors:

• Material Type: Different materials have different coefficients of thermal expansion. Metals generally expand more than ceramics.
• Temperature Change: The greater the temperature increase, the more significant the expansion.
• Initial Size of the Hole: A larger hole may experience a more noticeable change compared to a smaller one.

Conclusion

In summary, when a rectangular plate with a circular hole is heated, the size of the hole will indeed increase due to the thermal expansion of the surrounding material. This principle is fundamental in physics and engineering, illustrating how heat affects the physical properties of materials. Understanding these concepts is crucial for various applications, from construction to manufacturing.