Question Set 89

1.What does thermal diffusivity of metals signify.

Ans: Thermal diffusivity is associated with the speed of propagation of heat into solids during changes in temperature with time.

2.For conduction of heat, the instantaneous rate of heat flow is product of three factors. What are these ?

Ans: (i) Area of the section of the heat flow path, perpendicular to the direction of heat flow.

(ii) temperature gradient, i.e. change of temperature w.r.t. length of path.

(ii) Thermal conductivity of material.

3.How convective heat transfer is effected and on what factors it depends ?

Ans: Convective heat transfer is effected between a solid and fluid by a combination of molecular conduction within the fluid in combination with energy transport resulting from the motion of fluid particles. It depends on boundary layer configuration, fluid properties and temperature difference.

4.Which is the common element between brass and bronze ?

Ans: Copper.

5.What does following alloy designation indicate FG 250 ?

Ans: Grey cast iron with tensile strength of 250 MPa.

6.How is ceramic defined ?

Ans: It is a solid formed by combination of metallic and non-metallic elements.

7.Give one example of metal classified as per structure as BCC, FCC, HCP and CCP.

Ans: BCC (body centred cubic) structure—Molybdenum

FCC (face centred cubic) structure—Aluminium

HCP (hexagonal closed packed) structure—Zinc

CCP (cubic dosed packed) structure-Copper.

8.What is the name of solid solution of carbon in alpha iron and delta iron ?

Ans: Ferrite and austenite respectively.

9.Explain the difference between pearlite and cementile ?

Ans: Pearlite is eutectoid mixture of ferrite and cementile. Cementite is chemical compound of iron and carbon.

10.Give one example each of the following proportion of materials dimensional, physical, technological and mechanical.

Ans: Roughness, enthalpy, toughness, and hardness respectively.