Heat: To Change Or Not To Change?

A metal circular plate has a circular hole cut in the center of the plate. The plate is then heated and expands. What happens to the circular hole in the center of the plate.

• A. The circular hole would also expand, just like the plate.
• B. Even though the plate is expanding, the circular hole size would remain the same.
• C. The circular hole size would get smaller due the the plate expanding inward.
• D. Why would you cut a hole in a perfectly good plate?

See if you picked correctly.

Answer

Heat: To Change Or Not To Change? - Answer = A

Even though it might seem the expanding plate would force the hole to decrease in size, that is not what happens. Each and every molecule or atom moves away from its neighbor molecule or atom due to its increased vibrational energy because of the heat added to the plate. Thus the outer rim of the hole expands and moves outward increasing the size of the hole, exactly as if the hole were made of the same material as the solid plate.

Return to the question.