ELECTRICAL ENGINEERING MATERIALS

 1. The electrical conductivity of a material is the reciprocal of

A) Resistivity
B) Permeability
C) Permittivity
D) Reluctivity
Ans: A

2. The material used for filaments of electric lamps is
A) Copper
B) Aluminum
C) Tungsten
D) Nickel
Ans: C

3. Superconductivity is observed in materials at
A) High temperature
B) Room temperature
C) Very low temperature
D) All temperatures
Ans: C

4. The resistivity of a good conductor is of the order of
A) $10^{-6}$ Ω-m
B) $10^{-3}$ Ω-m
C) $10^{-8}$ Ω-m
D) $10^{-2}$ Ω-m
Ans: C

5. The property of a material to oppose magnetic flux is known as
A) Permeability
B) Reluctance
C) Permittivity
D) Conductivity
Ans: B

6. The most widely used magnetic material is
A) Aluminum
B) Silicon
C) Iron
D) Copper
Ans: C

7. The dielectric constant of vacuum is
A) 0
B) 1
C) Infinity
D) 8.85 × 10⁻¹² F/m
Ans: B

8. Which of the following is a ferromagnetic material?
A) Copper
B) Silver
C) Nickel
D) Bismuth
Ans: C

9. The main constituent of porcelain insulator is
A) Mica
B) Clay
C) Glass
D) Plastic
Ans: B

10. Which of the following materials has negative temperature coefficient of resistance?
A) Copper
B) Aluminum
C) Carbon
D) Iron
Ans: C

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11. The energy band gap in semiconductors is approximately
A) 0 eV
B) 1 eV
C) 5 eV
D) 10 eV
Ans: B

12. Hard magnetic materials are used for
A) Electromagnets
B) Transformers
C) Permanent magnets
D) Relays
Ans: C

13. Soft magnetic materials have
A) High coercivity
B) Low coercivity
C) High hysteresis loss
D) High retentivity
Ans: B

14. Copper is refined by
A) Electrolysis
B) Distillation
C) Filtration
D) None of these
Ans: A

15. The best conductor of electricity among metals is
A) Copper
B) Silver
C) Aluminum
D) Gold
Ans: B

16. Insulating materials have
A) Large number of free electrons
B) No free electrons
C) Few free electrons
D) Infinite conductivity
Ans: B

17. Carbon composition resistors have
A) Positive temperature coefficient
B) Negative temperature coefficient
C) Zero temperature coefficient
D) None of these
Ans: B

18. Mica is mainly used as
A) Conductor
B) Semiconductor
C) Dielectric
D) Magnetic material
Ans: C

19. The main purpose of doping in semiconductors is to
A) Increase the resistance
B) Reduce conductivity
C) Increase conductivity
D) None of these
Ans: C

20. The dielectric strength of air is about
A) 3 kV/mm
B) 30 kV/mm
C) 300 kV/mm
D) 0.3 kV/mm
Ans: A

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21. The resistivity of copper increases with
A) Increase in temperature
B) Decrease in temperature
C) Constant
D) None
Ans: A

22. Which material is used for fuse wire?
A) Copper
B) Aluminum
C) Tin-lead alloy
D) Silver
Ans: C

23. Insulating materials are
A) Paramagnetic
B) Diamagnetic
C) Ferromagnetic
D) Conductive
Ans: B

24. Which one of the following has the least resistivity?
A) Copper
B) Aluminum
C) Silver
D) Gold
Ans: C

25. Ferrites are used in
A) Transformer cores
B) Permanent magnets
C) Inductors and high-frequency devices
D) Heating elements
Ans: C

26. Thermistors are made of
A) Metals
B) Ceramics
C) Glass
D) Plastic
Ans: B

27. The Curie temperature is the temperature above which
A) A ferromagnetic material becomes paramagnetic
B) Superconductivity occurs
C) Resistivity becomes zero
D) None of these
Ans: A

28. The material used for making standard resistors is
A) Manganin
B) Copper
C) Aluminum
D) Nichrome
Ans: A

29. The main impurity in copper is
A) Iron
B) Sulphur
C) Zinc
D) Tin
Ans: B

30. The dielectric material in a capacitor serves to
A) Conduct electricity
B) Reduce capacitance
C) Store electrical energy
D) None of these
Ans: C

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31. Which of the following is not an insulator?
A) PVC
B) Mica
C) Silicon
D) Glass
Ans: C

32. The unit of permeability is
A) H/m
B) F/m
C) Ω-m
D) Wb/m²
Ans: A

33. A perfect dielectric has
A) Infinite resistivity
B) Zero resistivity
C) High conductivity
D) None
Ans: A

34. The material with lowest hysteresis loss is
A) Silicon steel
B) Cast iron
C) Nickel
D) Cobalt
Ans: A

35. Which of the following has highest conductivity?
A) Aluminum
B) Silver
C) Gold
D) Copper
Ans: B

36. The magnetic permeability of a vacuum is
A) 4π × 10⁻⁷ H/m
B) 8.85 × 10⁻¹² H/m
C) 10⁻³ H/m
D) None
Ans: A

37. Semiconductor materials include
A) Copper and aluminum
B) Silicon and germanium
C) Iron and steel
D) Silver and gold
Ans: B

38. For transformer cores, the material preferred is
A) Hard steel
B) Cast iron
C) Silicon steel
D) Copper
Ans: C

39. Which of the following materials has the highest resistivity?
A) Silver
B) Copper
C) Nichrome
D) Aluminum
Ans: C

40. The main function of dielectric in a capacitor is
A) To conduct current
B) To reduce leakage
C) To store energy in electric field
D) To increase resistance
Ans: C

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41. Conductivity is inversely proportional to
A) Mobility
B) Charge
C) Resistivity
D) Drift velocity
Ans: C

42. Which of the following materials is piezoelectric?
A) Quartz
B) Copper
C) Silicon
D) Iron
Ans: A

43. Magnetic susceptibility of diamagnetic materials is
A) Positive
B) Negative
C) Zero
D) Infinite
Ans: B

44. The magnetic material used in loudspeakers is
A) Ferrite
B) Soft iron
C) Nickel
D) Aluminum
Ans: A

45. The best material for electrical contacts is
A) Silver
B) Copper
C) Aluminum
D) Zinc
Ans: A

46. Which type of materials are used in thermocouples?
A) Conductors
B) Semiconductors
C) Dissimilar metals
D) Insulators
Ans: C

47. The magnetic flux density is measured in
A) Weber
B) Tesla
C) Henry
D) Gauss
Ans: B

48. Hysteresis loss is proportional to
A) Area of hysteresis loop
B) Volume of material
C) Magnetic field strength
D) None
Ans: A

49. The material used for heating elements is
A) Copper
B) Nichrome
C) Aluminum
D) Iron
Ans: B

50. Which of the following is a good dielectric material?
A) Mica
B) Copper
C) Iron
D) Nickel
Ans: A