Question

Thermal expansion

If we clamp the ends of a rod rigidly to prevent expansion or contraction and then change

the temperature, tensile or compressive stresses called thermal stresses develop. The rod

would like to expand or contract, but the clamps won't let it. The resulting stresses may

become large enough to strain the rod irreversibly or even break it.

Engineers must account for thermal stress when designing structures. Concrete highways

and bridge decks usually have gaps between sections, filled with a flexible material or

bridged by interlocking teeth, to permit expansion and contraction of the concrete.

Q3.1 A metallic sphere has a cavity of diameter D at its center. If the sphere is heated, the

diameter of the cavity will

a. Decrease

b. Increase

c. Remain unchanged

d. none of the above

Ans. ………………………………………………

Q3.2 When a solid metallic sphere is heated. The largest percentage increase occurs in it’s

a .Diameter

b. Surface area

c. Volume

d. density

Ans. ………………………………………………

Q3.3 A metallic circular disc having a circular hole at its center rotates about it axis passing

through the center and perpendicular to it plane. when the disc is heated

a. Its mass will decrease

b. Radius will decrease

c. Product of mass and square of the radius will increase

d. Product of mass and square of the radius will decrease

Which one of the above is correct?

Ans. ……………………………………………
​

Answer 1

1. Increase
2. Volume
3. product of mass and square of the radius will decrease