This set of Testing of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Scratch Hardness”.
1. What is the unit of scratch hardness?
a) Rc
b) Rb
c) Mohs
d) BHN
View Answer
Explanation: Scratch hardness is shown by unit Mohs. It is given from 1 to 10. Highest hardness is of a diamond.
2. Which material has the highest scratch hardness?
a) Talc
b) Diamond
c) Limestone
d) Quartz
View Answer
Explanation: Diamond has the highest scratch hardness. It is 10 Mohs. Talc and quartz have the hardness of 1 and 7 Mohs respectively.
3. Which material has the lowest scratch hardness?
a) Diamond
b) Gypsum
c) Talc
d) Topaz
View Answer
Explanation: Talc has the lowest scratch hardness. It is 1 Mohs. Diamond, gypsum and topaz have hardness 10, 2 and 8 Mohs respectively.
4. Which device is used to measure hardness in Mohs?
a) Gyro meter
b) Universal testing machine
c) Rockwell tester
d) Sclerometer
View Answer
Explanation: Scratch hardness is measured with the help of sclerometer. This device gives hardness in Mohs. A universal testing machine is used to measure tensile properties.
5. Scratch test is performed on ___________
a) Ceramics
b) Minerals
c) Soft metals
d) Steels
View Answer
Explanation: Scratch test is performed on minerals generally for example quartz, fluorite etc. Mineralogy is used for Mohs scale.
6. What is a right order of hardness?
a) Talc < Quartz < Fluorite
b) Calcite < Apatite < Topaz
c) Diamond < Topaz < Talc
d) Gypsum < Topaz < Quartz
View Answer
Explanation: Calcite, Apatite and Topaz have hardness 3,5 and 7 Mohs respectively. Diamond is the hardest on the list. While talc is softest with 1 moh hardness.
7. __________ is the measure of permanent deformation due to friction from a sharp object.
a) Rebound hardness
b) Toughness
c) Tensile strength
d) Scratch hardness
View Answer
Explanation: Scratch hardness is the measure of permanent deformation due to friction from a sharp object. It is widely used in mineralogy. Its most common unit is Mohs.
8. ___________ scale is widely used in mineralogy.
a) Brinell
b) Shore
c) Mohs
d) Knoop
View Answer
Explanation: Mohs scale is widely used in mineralogy. It is performed on sclerometer. Its range is 1 to 10 Mohs.
9. What is the hardness of quartz?
a) 3 Mohs
b) 5 Mohs
c) 7 Mohs
d) 9 Mohs
View Answer
Explanation: Quartz is the hard material. Its scratch hardness is 7 Mohs. Its chemical formula is SiO2.
10. What is the scratch hardness of steel?
a) 3 Mohs
b) 5.5 Mohs
c) 6.5 Mohs
d) 8 Mohs
View Answer
Explanation: Steel nail’s hardness is found in between 6 and 7 Mohs. It is 6.5 Mohs. It is harder than orthoclase but softer than quartz.
11. Scratch hardness is useful for coatings.
a) True
b) False
View Answer
Explanation: Scratch hardness test is also performed on coatings. It refers to force required to cut through the coating.
12. Sclerometer uses a harden steel ball as an indenter.
a) True
b) False
View Answer
Explanation: Sclerometer test is performed using a diamond. The width of a scratch made by a diamond under a fixed load. It is measured under a microscope.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
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