Electrical Engineering Materials MCQ PDF Download

21. Consider the following statements: At finite temperature, magnetic dipoles in a material are randomly oriented giving low magnetization. When magnetic field H is applied, the magnetization

1. increases with H.
2. decreases with H.
3. decreases with temperature for constant H.

Which of the statements given above is/are correct?
(a) 1 only.
(b) 2 only.
(c) 2 and 3.
(d) 1 and 3.

22. Consider the following statements regarding magnetic materials.

1. Relative permeability of water is 0.99999 and that of oxygen is 1.00002; hence water is diamagnetic and oxygen is paramagnetic material.
2. Ferrimagnetic material has no eddy current loss.
3. Permalloy and alnico are two examples of hard magnetic materials.
4. The magnetisation and applied electric field in ferromagnetic ‘materials are related nonlinearly.

Which of the statements given above are correct?
(a) 1, 2 and 3.
(b) 2, 3 and 4.
(c) 1, 3 and 4.
(d) 1, 2 and 4.

23. What is a material with equal, antiparallel atomic magnetic moments, known as

(a) Ferrimagnetic.
(b) Ferrite.
(c) Ferromagnetic.
(d) Antiferromagnetie.

24. A permeable substance is one

(a) which is strong magnetic.
(b) which is weak magnetic.
(c) which is a good conductor.
(d) through which magnetic lines of force can pass easily.

25. If the domain walls in a magnetic material can easily be moved, the material displays

(a) high flux density.
(b) high permeability.
(c) permanent magnetic behavior.
(d) high permittivity.

26. In which one of the following magnetic materials, is the net magnetic moment zero?

(a) Paramagnetic.
(b) Ferromagnetic.
(c) Ferrimagnetic.
(d) Anti-ferrimagnetic.

27. Which one of the following is the temperature below which certain materials are antiferromagnetic and above which they are paramagnetic?

(a) Curie temperature.
(b) Neel temperature.
(c) Transition temperature.
(d) Weiss temperature.

28. Temperature below which certain materials are anti-ferromagnetic is called

(a) Curie temperature.
(b) Neel temperature.
(c) Wein temperature.
(d) Debye temperature.

29. The spins in a ferrimagnetic material are

(a) all aligned parallel.
(b) partially aligned antiparallel without exactly cancelling out sublattice magnetism.
(c) randomly oriented.
(d) all aligned antiparallel such that the sublattice magnetism cancels out exactly.

30. Which one of the following is the correct statement? YIG and YAG are two types of crystals used extensively in technology and are

(a) non-magnetic and magnetic, respectively.
(b) magnetic and non-magnetic, respectively.
(c) both magnetic.
(d) both non-magnetic.

31. Ferromagnetic behavior is shown by those transition metals where the ratio of the atomic diameter to 3d orbital diameter is

(a) in the range of 0.5 to 1.
(b) in the range of 1 to 1.5.
(c) in the range of 1.5 to 2.
(d) greater than 2.

32. With increase in temperature, magnetic susceptibility of a ferromagnetic material will

(a) increase.
(b) decrease.
(c) increase initially and then decrease.
(d) remain constant.

33. Paramagnetic susceptibility of a material

(a) increases linearly with temperature.
(b) decreases linearly with temperature.
(c) increases linearly with (1/T).
(d) decreases linearly with (1/T).

34. Consider the following statements: Magnetic susceptibility

1. depends on the nature of the magnetic material.
2. is not dependent on the relative permeability of the medium.
3. cannot be determined by measuring the force exerted on a magnetic material when placed in a magnetic field.
4. can be determined from M-H curve.

Which of the above statements is/are correct?
(a) 1, 2, 3 and 4.
(b) 1 only.
(c) 1 and 4 only.
(d) 2 only.

35. Increase in percentage of carbon in carbon steels reduces

(a) resistivity.
(b) coercive force.
(d) permeability.
(d) retentivity.

36. …………cause(s) magnetic ageing.

(a) Mechanical vibrations.
(b) Temperature conditions.
(c) Presence of strong external fields.
(d) Variations in the external magnetic circuits.
(e) All of the above factors.

37. ………..is the most detrimental impurity in the magnetic materials.

(a) Sulphur
(b) Carbon
(c) Nitrogen
(d) None of these

38. Uniaxial anisotropy can be induced in bulk material by

(a) magnetic annealing.
(b) magnetic quenching.
(c) cold working.
(d) any of the above method.

39. Practically all organic substances are…………materials.

(a) paramagnetic.
(b) diamagnetic.
(c) ferromagnetic
(d) ferrimagnetic.

40. In a diamagnetic material, the effect of an applied magnetic field is that

(a) there is a net reduction in flux density.
(b) the induced magnetization is in opposition to the applied field.
(c) a net dipole moment is induced in the material.
(d) all of the above.
(e) none of these.