Design of Electrical Machines Questions and Answers Part-1

1. What is the basic property of electrical conducting materials?
a) allows the passage of current through the materials
b) blocks the passage of current through the materials
c) leaks the current through the materials
d) reverses the direction of current in the materials

Answer: a
Explanation: The basic property of conducting materials is to allow the flow of charges, and align them in a particular direction. The process is nothing but the flow of current in the materials.

2. What is the correct classification of the conducting materials?
a) low resistivity, low conductivity
b) low resistivity, high conductivity
c) high resistivity, high conductivity
d) medium resistivity, medium conductivity

Answer: b
Explanation: Resistivity is inversely proportional to the conductivity. So, if the material consists of high resistivity then it will obviously have low conductivity and vice versa.

3.Example of low resistivity material is _____________
a) silver
b) manganese
c) magnesium
d) tungsten

Answer: a
Explanation: Silver is the low resistivity material of all given materials. Tungsten is a part of high resistivity materials. The other two materials do not have a fixed resistivity and they vary with temperature.

4. Example of high resistivity material is ________________
a) copper
b) gold
c) aluminum
d) carbon

Answer: d
Explanation: Carbon is the highly resistivity material of all the materials. Whereas the other 3 materials are associated with low resistivity property in nature.

5. High resistivity material used in making the filaments of incandescent lamps.
a) true
b) false

Answer: a
Explanation: It is because to protect the lamps from getting over-heated. If the filaments get over-heated, it can lead to the bursting of the lamps.

6. What materials are used as conductors in the Transmission and Distribution sector?
a) copper
b) silver
c) tungsten
d) carbon

Answer: a
Explanation: Conductors in power system require less resistivity, highly malleable, highly ductile and less cost. Silver has all the above properties, but it is highly costly. So that makes copper highly suitable.

7. What are the properties of Conducting Materials with respect to temperature coefficient of resistance and tensile strength?
a) low temperature coefficient, low tensile strength
b) low temperature coefficient, high tensile strength
c) high temperature coefficient, low tensile strength
d) high temperature coefficient, high tensile strength

Answer: b
Explanation: The resistance of the material should not increase with temperature rise. This can lead to the loss of conduction property. High tensile strength allows in withstanding external disturbances, for smooth functioning.

8. What are the conditions of the conducting materials with respect to melting point and resistance to corrosion?
a) high melting point, low resistance to corrosion
b) low melting point, low resistance to corrosion
c) high melting point, high resistance to corrosion
d) low melting point, high resistance to corrosion

Answer: c
Explanation: High melting point, allows the materials to withstand low temperatures. High resistance to corrosion allows the material to avoid corrosion, to conduct effectively.

9. How should the conducting materials be in terms of malleability and ductility?
a) highly malleable, less ductile
b) less malleable, less ductile
c) highly malleable, highly ductile
d) less malleable, highly ductile

Answer: c
Explanation: The materials, having high malleability allow smooth conduction in transmission and distribution. The materials having high ductility help in producing wires flexibly for conduction.

10. Aluminum has high conductivity than Copper.
a) true
b) false

Answer: b
Explanation: Copper has high conductivity than Aluminum. The conductivity of Copper is 58.14*106 s/m and the conductivity of aluminum is 37.2*106 s/m.