# Casting Questions and Answers – Copper Alloys – 1

This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Copper Alloys”.

1. What is the general density of steel?
a) 6.67 g/cc
b) 7.87 g/cc
c) 8.77 g/cc
d) 5.77 g/cc

Explanation: A steel is basically a mixture of iron and carbon. The composition of iron varies according to the alloy, high alloy steels contain more amounts of carbon and low alloy steels contain less amount of carbon. The density of steels in general is found to be 7.87 g/cc.

2. What is the density of copper alloys?
a) 6.67 g/cc
b) 7.87 g/cc
c) 8.93 g/cc
d) 5.77 g/cc

Explanation: A steel is a mixture of iron and carbon and copper alloys are mixtures of mainly copper and a few other materials like zinc and nickel with it. The main copper alloys can be brass and bronze. The density of copper alloys in general is found to be 8.93 g/cc.

3. Which colour is obtained by copper alloys, when zinc is added to it?
a) Red
b) Blue
c) Silver
d) Yellow

Explanation: It is one of the most unusual properties of copper alloys, that on addition of different materials in them, there is a change observed in its appearance, that is, the colour of the mixture starts changing. On addition of zinc metal in copper, the colour of the mixture changes to yellow.

4. Which colour is obtained by copper alloys, when nickel is added to it?
a) Red
b) Blue
c) Silver
d) Yellow

Explanation: None.

5. What amount of impurity is allowed for copper to be used in electric applications?
a) 0.1%
b) 0.2%
c) 0.3%
d) 0.4%

Explanation: Copper and its alloys find themselves a variety of applications in the field of electrical and micro electrical works. For copper to be able to get used in electric appliances, the maximum impurity that can be allowed is 0.1%.
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6. Which of the following materials, on adding with copper, doesn’t increase its strength?
b) Silver
c) Sodium
d) Aluminium Oxide

Explanation: Copper originally does not possess a very high amount of strength. For properties of copper to be used, but with more strength, this copper needs to be mixed with certain material, which will provide it the required strength. Cadmium, silver and aluminium oxide are few of those materials which will aid in increasing its strength.

7. What is the tensile strength of cast manganese bronze?
a) 490 MPa
b) 759 MPa
c) 676 MPa
d) 324 MPa

Explanation: 759 mega pascals is the tensile strength of quenched and tempered copper-aluminium alloy. 676 MPa is the tensile strength of cold worked zinc. 324 MPa is the tensile strength of annealed zinc and 490 MPa is the tensile strength of cast manganese bronze.

8. What is the tensile strength of pure annealed copper?
a) 324 MPa
b) 676 MPa
c) 759 MPa
d) 209 MPa

Explanation: None.

9. Copper alloys are mostly hot treated?
a) True
b) False

Explanation: For properties of copper to be used, but with more strength, this copper needs to be mixed with certain material, which will provide it the required strength. Cadmium, silver and aluminium oxide are few of those materials which will aid in increasing its strength. This process of increasing strength is done by treating the alloy through cold working.

10. Iron needs higher temperature ranges for its extraction.
a) True
b) False

Explanation: The metal copper has its occurrence in large quantities. This material can be successfully extracted from the mines before the iron is extracted, the reason being, copper extraction happens at lower temperatures.

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