MATERIAL SCIENCE MCQ SET 4
Q1. The main purpose of tempering steel is to:
A) Increase brittleness
B) Reduce hardness and increase toughness
C) Convert ferrite to austenite
D) Produce martensite
Answer: B) Reduce hardness and increase toughness
Explanation: Tempering reduces brittleness of quenched steel while retaining reasonable hardness.
Q2. Which property of ceramics is typically low?
A) Hardness
B) Electrical conductivity
C) Compressive strength
D) Thermal stability
Answer: B) Electrical conductivity
Explanation: Ceramics are generally insulators due to their ionic/covalent bonding.
Q3. The percentage of carbon in mild steel is approximately:
A) 0.05โ0.2%
B) 0.2โ0.6%
C) 1โ2%
D) 2โ6%
Answer: B) 0.2โ0.6%
Explanation: Mild steel has low carbon content, making it ductile and easy to weld.
Q4. Which of the following increases hardness by blocking dislocation movement?
A) Annealing
B) Work hardening
C) Normalizing
D) Quenching
Answer: B) Work hardening
Explanation: Plastic deformation increases dislocation density, strengthening the metal.
Q5. The main constituent of brass is:
A) Copper and Tin
B) Copper and Zinc
C) Copper and Nickel
D) Aluminum and Copper
ย Answer: B) Copper and Zinc
Explanation: Brass is a copper-zinc alloy, commonly used in musical instruments and fittings.
Q6. Which of the following is a ferromagnetic metal?
A) Aluminum
B) Iron
C) Copper
D) Lead
Answer: B) Iron
Explanation: Iron has unpaired electrons in 3d orbitals, giving ferromagnetic properties.
Q7. The process of slow cooling steel in still air to refine grains is called:
A) Quenching
B) Annealing
C) Normalizing
D) Tempering
Answer: C) Normalizing
Explanation: Normalizing refines grain structure and improves mechanical properties.
Q8. The toughness of a material can be measured using:
A) Rockwell hardness test
B) Brinell hardness test
C) Charpy impact test
D) Tensile test
Answer: C) Charpy impact test
Explanation: Impact tests measure energy absorbed before fracture, indicating toughness.
Q9. Polymers are primarily:
A) Metallic materials
B) Inorganic compounds
C) Organic macromolecules
D) Ceramics
Answer: C) Organic macromolecules
Explanation: Polymers consist of long chains of organic molecules; examples include plastics and rubbers.
Q10. The purpose of adding chromium to steel is to:
A) Increase ductility
B) Increase corrosion resistance
C) Reduce hardness
D) Reduce melting point
Answer: B) Increase corrosion resistance
Explanation: Chromium forms a passive oxide layer that protects steel from rust.
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