Question

In superficial expansion of solids

A. Increase in thickness is negligible as compared to increase in length and breadth

B. Increase in length and breadth is negligible as compared to increase in thickness

C. Both (A) and (B)

D. None of the above

Answer 1

Hint: We all know expansion is nothing but increase in volume. But superficial expansion is also an expansion but expansion dimension will be only length and breadth that is area and not volume. You can memorize expansion as the process that happens in heating.

Complete answer:

Take an example of the rod. When it gets heated, its length and breadth get expanded. This is nothing but superficial expansion. an increase in the dimension(only length and breadth) of the body because of heating is known as superficial expansion. So an increase in area, that is, length and bread on heating is called a superficial expansion.

So, in the case of a thin sheet or lamina, superficial expansion takes place. Also, the increase in thickness of the sheet is negligible compared to the increase in the length and the breadth of the sheet. 

Therefore, the correct answer is option (A).

Note: There are lots of examples which do possess superficial expansion. Some materials or solid get contracted on heating while some get expanded. In superficial expansion, only length and breadth are increasing; that is an area, not volume.