A square shaped hole is punched in a metal sheet whose linear thermal expansion coefficient is 1 × 10^-3 per °C. The size of the hole will decrease by 10%, when

The correct answer is The sheet is heated by 100 ºC.

Key Points

• When the sheet is heated by 100 ºC, the linear expansion coefficient (1 × 10^-3 per ºC) will cause the dimensions of the square hole to increase.
• For the square hole, the linear expansion in each direction (length and width) will be the same.
• The increase in size will be proportional to the temperature change and the expansion coefficient.
• Since the expansion is linear, heating the sheet by 100 ºC will result in a 10% increase in the size of the square hole.

Important Points

• Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature.
• The linear expansion coefficient is a material property that indicates how much a material expands per unit length for a unit increase in temperature.
• In general, heating causes expansion while cooling causes contraction.
• For a square or rectangular hole in a sheet, the expansion or contraction is uniform in all directions.