MAGNETIC PARTICLES TESTING (MT)
2.1 Magnetic Particles Testing Level 1 (MT-1)
2.1.1 Magnetic Particles Testing Level 1 (MT-1) General Examination
1. Magnetic particles testing is most likely to find subsurface discontinuities in:
(a) Soft steels with high permeability
(b) Soft steels with low permeability
(c) Hardened steels with low permeability
(d) Hardened steels with high permeability
2. Which of the following is not an advantage of magnetic particles testing?
(a) Fast and simple to perform
(b) Can detect discontinuities filled with foreign material
(c) Most reliable for finding surface cracks in all types of material
(d) Works well through a thin coat of paint
3. Which of the following does not represent a limitation of magnetic particle testing?
(a) The type of materials which may be effectively tested
(b) The directionality of the magnetic field
(c) The need for demagnetization
(d) The ability to detect discontinuities filled with foreign material
4. The most effective NDT method for locating surface cracks in ferromagnetic materials
is:
(a) Ultrasonic testing
(b) Radiographic testing
(c) Magnetic particle testing
(d) Liquid penetrant testing
5. Which of the following may cause magnetic particle test indications?
(a) A joint between two ferromagnetic materials of different permeability
(b) A shrink fit joint in ferromagnetic materials
(c) A brazed joint in ferromagnetic materials
(d) All of the above
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6. A discontinuity which is produced during solidification of the molten metal is called:
(a) Inherent
(b) Processing
(c) Service
(d) None of the above
7. Pipe would be classified as what type of discontinuity?
(a) Inherent
(b) Processing
(c) Service
(d) None of the above
8. A seam would be classified as what type of discontinuity?
(a) Inherent
(b) Processing
(c) Service
(d) None of the above
9. A lamination in steel plate would be classified as what type of discontinuity?
(a) Inherent
(b) Processing
(c) Service
(d) None of the above
10. An internal rupture caused by working steel at improper temperatures is called a:
(a) Lap
(b) Cold shut
(c) Forging burst
(d) Slag inclusion
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11. Cracks which are caused by alternating stresses above a critical level are called:
(a) Stress corrosion cracks
(b) Cycling cracks
(c) Critical cracks
(d) Fatigue cracks
12. Cracks which are caused by a combination of tensile stress and corrosion are called:
(a) Stress corrosion cracks
(b) Cycling cracks
(c) Critical cracks
(d) Fatigue cracks
13. Which of the following are ferromagnetic materials?
(a) Aluminium, iron, copper
(b) Iron, copper, nickel
(c) Copper, aluminium, silver
(d) Iron, cobalt, nickel
14. The reverse magnetising force necessary to remove a residual magnetic field from a
test piece after it has been magnetically saturated is called:
(a) Hysteresis
(b) Coercive force
(c) Demagnetising flux
(d) Reverse saturation
15. Magnetic lines of force enter and leave a magnet at:
(a) Saturation
(b) L/D ratios of greater than 4 to 1
(c) Flux concentration points
(d) Poles
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16. The ease with which a magnetic field can be established in a test piece is called:
(a) Reluctance
(b) Retentivity
(c) Permeability
(d) Electromagnetism
17. Opposition to establishment of a magnetic field is called:
(a) Reluctance
(b) Retentivity
(c) Permeability
(d) Electromagnetism
18. The ability of a material to remain magnetic after the magnetising force is removed is
called:
(a) Reluctance
(b) Retentivity
(c) Permeability
(d) Electromagnetism
19. A magnetic field which is contained completely within the test piece is called a:
(a) Confined field
(b) Longitudinal field
(c) Circular field
(d) Saturated field
20. Which of the following produces a circular field?
(a) Coil
(b) Head shot
(c) Yoke
(d) All of the above
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21. A technique used to find transverse discontinuities at the ends of longitudinally
magnetised bars by the use of transient currents is called:
(a) A coil technique
(b) A fast break technique
(c) A yoke technique
(d) A head shot
22. A leakage field is strongest when a discontinuity interrupts the magnetic flux lines at
an angle of:
(a) Zero degrees
(b) 45 degrees
(c) 90 degrees
(d) 180 degrees
23. The best method of inducing a circular field in a tube is by a:
(a) Central conductor
(b) Head shot
(c) Coil
(d) Prod technique
24. Magnetic flux density is zero at:
(a) The inside surface of a tube magnetised with a central conductor
(b) The outside surface of a tube magnetised with a central conductor
(c) The outside surface of a bar magnetised with a head shot
(d) The centre of a bar magnetised with a head shot
25. Magnetic flux density is highest at:
(a) The outside surface of a non-ferromagnetic tube magnetised with a central
conductor
(b) The inside surface of a non-ferromagnetic tube magnetised with a central
conductor
(c) The outside surface of a ferromagnetic tube magnetised with a central
conductor
(d) The inside surface of a ferromagnetic tube magnetised with a central conductor
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26. An important consideration when using a direct contact method is:
(a) Lifting power of the yoke
(b) Coil diameter
(c) Preventing arc burns
(d) Field strength adjacent to the coil inside diameter
27. A prod method would be most sensitive to cracks:
(a) Parallel to a line connecting the prod contact points
(b) Tangential to a radius from each prod contact point
(c) Perpendicular to a line connecting the prod contact points
(d) Perpendicular to the long axis of the coil
28. When using prods, arc burns may be caused by which of the following?
(a) Dirty contact tips
(b) Inadequate pressure
(c) Too large a magnetic current
(d) All of the above
29. The important difference between AC and DC current for magnetic particle testing
purposes is:
(a) The skin effect caused by DC adds mobility to the magnetic particles
(b) The resulting AC magnetic fields are more difficult to demagnetize
(c) The DC magnetic fields are more penetrating
(d) The AC magnetic fields are stronger
30. The ‘skin’ effect would be most noticeable in which of the following?
(a) A magnetic conductor carrying a DC current
(b) A nonmagnetic conductor carrying a DC current
(c) A magnetic conductor carrying a 50 Hz AC current
(d) A nonmagnetic conductor carrying a 50 Hz AC current
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31. The most common source of DC current for magnetic particle testing is:
(a) Motor generators
(b) Rectified AC
(c) Storage batteries
(d) None of the above
32. Fields generated in ferromagnetic material with AC current are useful for locating:
(a) All discontinuities
(b) Surface cracks
(c) Subsurface discontinuities
(d) Internal porosity
33. A common rule of thumb to use for current required in circular magnetisation:
(a) 1000 amps/25mm of diameter
(b) 1000 ampere turns/25mm of diameter
(c) 1000 amps/25mm of prod spacing
(d) None of the above
34. The formula, NI = 45000/(L/D), is used to calculate the proper magnetising current
for:
(a) Prod magnetization
(b) A head shot
(c) A central conductor
(d) Coil magnetisation
35. The formula, NI = 45000/(L/D), gives proper magnetising current for a coil, regardless
of coil size as long as:
(a) The test piece is not larger than 1/10 the cross sectional area of the coil
(b) AC current only is used
(c) The test piece essentially fills the coil
(d) The test piece is held tightly against the coil
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36. For direct contact magnetising methods, the magnetic field is oriented in what
direction relative to the current direction?
(a) Parallel
(b) At 45 degrees
(c) At 90 degrees
(d) At 180 degrees
37. For direct contact magnetising methods, current should be flowing in what direction
relative to expected discontinuities?
(a) Parallel
(b) At 45 degrees
(c) At 90 degrees
(d) At 180 degrees
38. What is the magnetic field strength at the surface of a 100 mm diameter bar as
compared to that at the surface of a 50 mm diameter bar, each carrying 1000 amps of
current?
(a) Twice
(b) One half
(c) One quarter
(d) Four times
39. What is the magnetic field strength at the surface of a 25mm diameter bar as compared
to that at the surface of a 50mm diameter bar, each carrying 1000 amps of current?
(a) Twice
(b) One half
(c) One quarter
(d) Four times
40. The magnetic field outside a conductor decreases:
(a) Exponentially
(b) In a linear manner
(c) Inversely with distance
(d) Inversely with the square of distance
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41. How is the magnetic field strength at the surface of a magnetic conductor having
permeability, μ, related to the magnetic field strength, F, at the surface of a
nonmagnetic conductor carrying the same current?
(a) F × μ
(b) Same
(c) F/μ
(d) Not related
42. Compared to the magnetic field strength at the outer surface, the magnetic field
strength, at the centre of a hollow, nonmagnetic conductor carrying DC current is:
(a) I/D
(b) The same
(c) Zero
(d) Need more information to determine
43. How is the magnetic field strength, F, just outside a magnetic conductor having
permeability, μ, related to that just outside a nonmagnetic conductor of the same size,
carrying the same current?
(a) F × μ
(b) Same
(c) (F)/μ
(d) Not related
44. Which of the following describes the shape of particles used for dry magnetic particle
testing?
(a) Spherical
(b) Angular
(c) Elongated
(d) Mixture of elongated and globular
45. Which of the following particles would be most sensitive?
(a) Wet
(b) Dry
(c) Depends on the test piece permeability
(d) None of the above
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46. Which of the following colours is readily available for magnetic particle test powder?
(a) Red
(b) Gray
(c) Black
(d) All of the above
47. A magnetic particle testing technique in which the test piece is magnetised and
magnetic particles applied after the magnetising force has been removed is called the:
(a) Magnetic method
(b) Continuous method
(c) Residual method
(d) Discontinuous method
48. Which of the following characteristics would be most important in a test piece which
is to be tested using the residual method?
(a) High rententivity
(b) High permeability
(c) Low reluctance
(d) Low permeability
49. The wet method is superior to dry particles for detecting:
(a) Subsurface discontinuities
(b) Fine surface cracks
(c) Open surface cracks
(d) None of the above
50. Selection of magnetic particle colour is based on:
(a) Optimum performance of magnetic particle/developer
(b) Colour of inspection light available
(c) Obtaining maximum contrast with the test piece background
(d) Optimum colour response of the human eye
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51. The residual method is applicable to:
(a) Surface discontinuities only
(b) Subsurface discontinuities only
(c) Either surface or subsurface discontinuities
(d) All but tight surface cracks
52. Highest sensitivity to fine surface cracks would be obtained by which of the following
techniques?
(a) Residual field, wet method
(b) Residual field, dry method
(c) Continuous field, wet method
(d) Continuous field, dry method
53. A residual field is always less than a continuous field because?
(a) The magnetic field, as shown by a hysteresis curve, is zero when there is no
magnetising force
(b) The magnetic field, as shown by a hysteresis curve, is less when there is no
magnetising force
(c) The magnetic field, as shown by a hysteresis curve, is greater when there is no
magnetising force
(d) None of the above
54. Where possible, circular magnetisation is preferable to longitudinal magnetization
because:
(a) Less current is required
(b) Stronger fields are obtained
(c) Fewer confusing secondary poles are produced
(d) None of the above is true
55. Which of the following is a disadvantage of the dry method?
(a) Ease of application with portable equipment
(b) Superior sensitivity for fine surface cracks
(c) Good particle mobility with AC and HWDC
(d) Good sensitivity for subsurface discontinuities
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56. Which of the following is an advantage of the dry method
(a) Good sensitivity for subsurface discontinuities
(b) Faster than wet method for quantities of small test pieces
(c) Easily applied in an automated system
(d) Easy coverage of surfaces of irregularly shaped test pieces
57. Loss of fine particle sizes due to re-use of dry particles would probably lead to:
(a) Loss of sensitivity to larger discontinuities
(b) Loss of sensitivity to finer discontinuities
(c) Unpredictable results
(d) Slower inspection speeds
58. Which of the following is a disadvantage of the wet method?
(a) It is the most sensitive method for detection of very fine surface cracks
(b) Rapid testing of large quantities of small test pieces
(c) Readily adaptable to mechanised equipment
(d) Excellent detection of completely subsurface discontinuities
59. Which of the following is an advantage of the wet method?
(a) Excellent detection of completely subsurface discontinuities
(b) Ease of bath recovery and re-use
(c) Low flash point ensures freedom from fire hazards
(d) Relatively clean and easy to work with
60. The primary reason for using water rather than oil as a suspension medium for wet
method baths is that:
(a) Water is more chemically inert than oil
(b) Bath flammability hazards are eliminated
(c) Water has the capability to dissolve the needed rust inhibitors
(d) Water baths may be used at lower temperatures than oil baths
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61. A disadvantage of fluorescent magnetic particles is:
(a) Darkened area and black light are required
(b) Abnormally high sensitivity
(c) Only dry particles are available
(d) Only wet concentrate is available
62. A common physiological effect of black light inspection on the inspector is:
(a) Burned retinas of the eyes
(b) Rejected cornea syndrome
(c) Eye fatigue
(d) Retarded iris control
63. A common physiological effect of black light inspection on the inspector is:
(a) Burned retinas of the eyes
(b) Rejected cornea syndrome
(c) Eyeball fluorescence
(d) Retarded iris control
64. Which of the following represents ultraviolet light of wavelengths which are
potentially injurious (1 Å = 10-10m)
(a) 2000 to 3200 Å
(b) 3200 to 4000 Å
(c) 4000 to 4600 Å
(d) 4600 to 5200 Å
65. Dyes which receive light at one wavelength and re-emit light of another wavelength
are called:
(a) L.E.Ds
(b) Phosphorescent
(c) Luminescent
(d) Fluorescent
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66. Most fluorescent dyes used for magnetic particle testing fluoresce what colour?
(a) Blue green
(b) Yellow green
(c) Blue black
(d) Red orange
67. The best available source of black light for inspection is:
(a) The mercury vapour lamp
(b) The fluorescent tube
(c) The incandescent bulb
(d) Sunlight
68. Which of the following would be likely to cause variations in the output of an
inspection black light?
(a) Voltage fluctuations
(b) Aged bulb
(c) Dirty filter
(d) All of the above
69. The temperature above which steels become nonmagnetic is called the:
(a) Zero retentivity
(b) Curie point
(c) Demagnetisation temperature
(d) Random polar point
70. The temperature above which most soft steels become nonmagnetic is about:
(a) 440ºC (770oF)
(b) 523ºC (975ºF)
(c) 626ºC (1160ºF)
(d) 754ºC (1390ºF)
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71. The most common method of demagnetising small test pieces is:
(a) Heat treatment
(b) Shot peening
(c) Passing through an AC coil
(d) Direct contact with AC current
72. Demagnetisation with reversing DC is more effective than AC because:
(a) DC is more penetrating
(b) Demagnetisation is assisted by the skin effect
(c) DC is more direct
(d) Not true - AC is more effective
73. The type of discontinuity which magnetic particle testing most effectively locates is:
(a) Slag inclusions
(b) Magnetic writing
(c) Porosity
(d) Surface cracks
74. An indication which is formed when two pieces of magnetised steel come in contact
with each other is called:
(a) A metallurgical discontinuity
(b) Magnetic writing
(c) Magnetic transfer
(d) A ferromagnetic notch
75. Magnetic particle test indications which are due to cold work can best be removed by:
(a) Demagnetisation
(b) Using a lower current
(c) Re-crystallisation
(d) Heat treating
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76. Which of the following might cause non-relevant indications?
(a) Over magnetisation
(b) Indications at the edges of a braze joint
(c) A joint between hard and soft steels
(d) All of the above
77. An inspection for surface and subsurface discontinuities in ferromagnetic welds would
best be accomplished by which of the following techniques?
(a) Prods
(b) AC yoke
(c) Half wave DC yoke
(d) None of the above
78. A continuous linear indication along the centre of a fillet weld would most likely be a:
(a) Crater crack
(b) Overlap
(c) Root indication
(d) None of the above
79. Wet magnetic particle bath strength is checked by which of the following?
(a) Specific gravity
(b) Optical density
(c) Settling test
(d) None of the above
80. Which of the following describes the best technique for applying dry magnetic
particles to a test piece?
(a) Dip the test piece in a tank of dry particles while current is flowing
(b) Apply with an electrostatic spray gun at approximately 30 PSIG
(c) Gently pour the powder onto the test piece
(d) Shake or dust the powder onto the test piece with minimum velocity
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81. An advantage of AC equipment over DC is:
(a) AC is more penetrating
(b) AC is less hazardous
(c) AC makes the magnetic particles more mobile on the test surface
(d) AC equipment is heavier than DC
82. When the orientation of likely discontinuities is unknown, what is the minimum
number of magnetising operations required to perform an adequate test?
(a) 1
(b) 2
(c) 3
(d) None of the above
83. Maximum practical prod spacing is about:
(a) 100 mm
(b) 200 mm
(c) 300 mm
(d) 450 mm
84. Magnetic lines of flux which are parallel to a discontinuity produce:
(a) Strong indications
(b) Weak indications
(c) No indications
(d) Fuzzy indications
85. The area of maximum induced field strength using a yoke is:
(a) At the north pole of the yoke
(b) At the south pole of the yoke
(c) The area directly between the poles
(d) On the outside of the pole pieces
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86. A minimum of external poles are produced by what type of magnetisation?
(a) Continuous
(b) Residual
(c) Circular
(d) Longitudinal
87. A split coil would most likely be used with a:
(a) DC yoke
(b) Split phase AC yoke
(c) Stationary magnetic particle unit
(d) Portable magnetic particle unit
88. The most common harmful effect of exposure to black light is:
(a) Eyeball fluorescence
(b) Burned retinas
(c) Skin burns
(d) None of the above
89. Which of the following types of magnetic fields may be present without any external
evidence?
(a) Circular
(b) Longitudinal
(c) Secondary
(d) Tertiary
90. A residual circular field may be objectionable because:
(a) Grinding may produce cracks
(b) Machining may create external poles
(c) Heat treating may lead to tight surface cracks
(d) All of the above
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91. Which of the following is a disadvantage of magnetic particle testing?
(a) Fast and simple to perform
(b) Can detect discontinuities filled with foreign material
(c) Most reliable for finding surface cracks in all types of metals
(d) Works well through a thin coat of paint
2.1.2 Magnetic Particles Testing Level 1 (MT-1) Specific Examination
1. The primary reason for using water rather than oil as a suspension medium for wet
method baths is that
(a) Water is more chemically inert than oil
(b) Bath flammability hazards are eliminated
(c) Water has the capability to dissolve the needed rust inhibitors
(d) Water baths may be used at a lower temperature than oil baths
2. Wet magnetic particle strength is checked by which of the following?
(a) Specific gravity
(b) Optical density
(c) Settling test
(d) None of the above
3. A residual circular field may be objectionable because:
(a) Grinding may produce heat cracks
(b) Machining may create external poles
(c) Heat treating may lead to tight surface cracks\
(d) All of the above
4. A prod method would be most sensitive to cracks:
(a) Parallel to a line connecting the prod contract points
(b) Tangential to a radius from each prod contact point
(c) Perpendicular to a line connecting the prod contact points
(d) Perpendicular to the long axis
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5. Highest sensitivity to fine surface cracks would be obtained by which of the following
techniques?
(a) Residual field, wet method
(b) Residual field, dry method
(c) Continuous field, wet method
(d) Continuous field, dry method
6. Maximum practical prod spacing for a 2000 amp unit is about:
(a) 100 mm
(b) 200 mm
(c) 300 mm
(d) 450 mm
7. Demagnetisation with reversing DC is more effective than AC because:
(a) DC is more penetrating
(b) Demagnetisation is assisted by the skin effect
(c) DC is more direct
(d) Not true-AC is more effective
8. Fluorescent magnetic particle indications should be inspected under
(a) Fluorescent light
(b) Any light
(c) Black light
(d) Red light
9. A discontinuity which is produced during solidification of the molten metal is called:
(a) Inherent
(b) Processing
(c) Service
(d) None of the above
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10. Cracks which are caused by a combination of tensile stress and corrosion are called:
(a) Intergranular stress corrosion cracking
(b) Cycling cracks
(c) Stress corrosion cracking
(d) Fatigue cracks
11. The type of discontinuity potentially most harmful to the useful life of a part is:
(a) Slag inclusions
(b) Magnetic writing
(c) Porosity
(d) Surface cracks
12. Magnetic particle test indications which are due to cold work can best be removed by:
(a) Demagnetisation
(b) Using a lower current
(c) Using penetrant testing
(d) Re-heat treating
13. Which of the following might cause non relevant indications?
(a) Magnetic writing
(b) Indications at the edges of a braze joint
(c) A joint between hard and soft steels
(d) All of the above
14. A continuous linear indication along the edge of a new fillet weld would most likely
be a:
(a) Crater crack
(b) Fatigue crack
(c) Stress corrosion crack
(d) Heat affected zone hydrogen crack
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15. Ferromagnetic material is:
(a) Strongly attracted by a magnet
(b) Capable of being magnetized
(c) Both (a) and (b)
(d) Not capable of being magnetized
16. The retentivity of a material describes:
(a) The ease with which it can be magnetized
(b) The depth of the magnetic field in the part
(c) The length of time required to demagnetise it
(d) The ability to retain the magnetic field
17. Which of the following can be magnetised?
(a) Iron
(b) Nickel
(c) Cobalt
(d) All of the above
18. The magnetic field is strongest when:
(a) The magnetising voltage is flowing
(b) The magnetising current is flowing
(c) The material exhibits high coercive forces
(d) The magnetising current is not flowing
19. The unit usually used to denote flux density is the:
(a) Gauss
(b) Henry
(c) Farad
(d) Ampere
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20. Which statement is true when related to magnetic lines of force?
(a) They never cross
(b) They are most dense at the poles of a magnet
(c) They seek the path of least resistance
(d) All of the above
21. Magnetic lines of force:
(a) Travel in straight lines
(b) Form a closed loop
(c) Are randomly oriented
(d) Overlay in highly ferromagnetic materials
22. The areas on a magnetised part from which the magnetic field is leaving or returning
into the part are called:
(a) Salient points
(b) Defects
(c) Magnetic poles
(d) Nodes
23. The magnetism which remains in a piece of magnetisable material after the
magnetising force has been removed is called the:
(a) Tramp field
(b) Residual field
(c) Damped field
(d) Permanent field
24. Which technique is the most sensitive?
(a) Continuous
(b) Residual
(c) Interrupted
(d) Counter current
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25. The point at which the magnetism in a material cannot be increased even though the
magnetising force continues to increase is known as the:
(a) Salient pole
(b) Saturation point
(c) Residual point
(d) Remnant point
26. An electric current through a copper wire:
(a) Creates a magnetic field around the wire
(b) Creates magnetic poles in the wire
(c) Magnetises the wire
(d) Does not create a magnetic field
27. A longitudinal surface crack in a circularly magnetised part will cause:
(a) The magnetic field to die out
(b) A decrease in permeability
(c) A magnetic leakage field
(d) A current to flow
28. The type of current that is best suited to detect surface discontinuities is:
(a) DC
(b) AC
(c) Pulsating DC
(d) Half wave
29. Retentivity:
(a) Represents the ability to induce magnetism in a ferromagnetic body by an
outside magnetising force
(b) Represents the ability of a material to resist the establishment of magnetic flux
within it
(c) Represents the ability of a material to retain a portion of the magnetic field set
up in it after the magnetising force has been removed
(d) Is not a term used in magnetic particle testing
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30. Demagnetisation:
(a) May be easy or difficult depending on the type of material
(b) Is easy for materials having a high coercive force
(c) Is always most difficult in materials retaining a high residual field
(d) All of the above answers are correct
31. What rule describes the direction of current flow (+ to -) when lines of magnetic force
surround a conductor?
(a) Left hand rule
(b) Right hand rule
(c) Flux rule
(d) Reluctance rule
32. The proper number of ampere-turns for a given test specimen is determined by:
(a) Its length
(b) The material and its diameter
(c) Both the length and the material
(d) Its diameter and length
33. An electrical yoke produces:
(a) A longitudinal field
(b) A circular field
(c) Alternating fields
(d) A swinging field
34. In longitudinal magnetisation the proper term for calculating magnetising force is:
(a) Amperes
(b) Ampere-turns
(c) Watts
(d) Ohms
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35. The amount of amperage used for magnetic particle inspection using the prod method
is determined from the:
(a) Type of material
(b) Distance between the prods
(c) Diameter of the part
(d) Total length of the part
36. Which of the following is the most effective method for the detection of extremely
deep-lying defects:
(a) Dry residual method using DC surge
(b) Wet continuous method using half wave rectified current
(c) Wet residual method
(d) Dry continuous method using half wave rectified current with prods
37. What method provides greater sensitivity, particularly in locating subsurface
discontinuities?:
(a) Continuous
(b) Residual
(c) Circular
(d) Longitudinal
38. Which type of current has a ‘skin effect’:
(a) AC
(b) DC
(c) Half wave rectified
(d) Full wave rectified
39. When using the wet continuous method, the flow of suspension from the hose should
be shut off:
(a) Immediately after applying the current
(b) Immediately before applying the current
(c) While the current is flowing
(d) Thirty seconds before applying the current
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40. The area of maximum induced field strength using a yoke is:
(a) At the north pole of the yoke
(b) At the south pole of the yoke
(c) The area directly between the poles
(d) on the outside of pole pieces
41. The strongest magnetic field in a coil is at the:
(a) Outside edge
(b) Inside edge
(c) Centre
(d) End
42. What equipment is used to determine if a part has been demagnetised?
(a) A magnet on the part
(b) A field meter
(c) A survey meter
(d) Careful observation for clinging magnetic particles
43. Which of the following will best define surface cracks?
(a) Half wave rectified AC
(b) DC
(c) AC
(d) Surge current
44. Applying the theory of the ‘Right Hand Rule’, a longitudinal surface defect in a round
bar is detected by ‘current passing in a direction parallel to the direction of expected
defects’ because:
(a) The current direction is in line with the defect
(b) The magnetic field is at right angles to the defect
(c) It makes no difference
(d) The magnetic field is parallel to the defect
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45. Why are magnetic particles available in different colours?
(a) For colour contrast with the part surface
(b) To enhance the detection of indications
(c) For both a and b
(d) Different colours are used with different magnetic flux values
46. A magnetic particle build-up from a discontinuity is strongest when the discontinuity
is oriented:
(a) 180o to the magnetic field
(b) 45o to the magnetic field
(c) 90o to the magnetic field
(d) 90o to the current flow
47. Why is it preferable to disassemble parts before magnetic particle inspection?
(a) Disassembly makes all surface areas visible
(b) Interfaces will create leakage fields which may confuse the inspection
(c) It is usually easier to handle the disassembled parts
(d) All of the above
48. Fluorescent magnetic particle indications should be inspected under
(a) Fluorescent light
(b) Any light
(c) Black light
(d) Neon light
49. Why should one avoid using a high velocity flow of a wet testing media over the test
area
(a) It may wash away a fine or lightly held indication
(b) This is not a problem
(c) It may splash particle into eyes
(d) None of the above are correct
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50. What are the three causes of non-relevant indications?
(a) Lack of fusion, change of section thickness, grinding cracks
(b) Change of section thickness, very high amperage, drilled hole near surface
(c) Very high amperage, drilled hole near surface, blow holes
(d) Drilled hole near surface, very high amperage, lack of fusion
51. Magnetic particle inspection is not a reliable method of detecting
(a) Laps
(b) Deep seated cavities
(c) Cracks
(d) Seams
52. A defect open to the surface produces an indication which is
(a) Sharp and distinct
(b) Wide and indefinite
(c) Criss-cross
(d) High and fuzzy
53. Wet magnetic bath strength is checked by which of the following
(a) Specific gravity
(b) Optical density
(c) Settling test
(d) None of the above
54. When preparing a bath it is important to have the bath strength at a proper level, as too
many particles can result in:
(a) Lowering the test amperage
(b) Having to increase the magnetising current
(c) Masking the indications
(d) None of the above
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55. Magnetic particle is a non-destructive examination method used for:
(a) Locating surface discontinuities
(b) Near surface discontinuities
(c) Both a and b
(d) Material separation
56. A part is adaptable to magnetic particle inspection if
(a) It is attached to an electrostatic field
(b) The material is ferromagnetic
(c) The material is non-ferrous
(d) The material is an electric conductor
57. The permeability of a material describes:
(a) The ease with which it can be magnetized
(b) The depth of the magnetic field in the part
(c) The length of time required to demagnetise it
(d) The ability to retain the magnetic field
58. If a crack exists in a circular magnet, the attraction of magnetic particles to the crack is
caused by:
(a) A coercive force
(b) A leakage field
(c) A Doppler effect
(d) A high reluctance at the crack
59. The flux within and surrounding a magnetised part or around a conductor carrying a
current is known as:
(a) Saturation point
(b) Magnetic field
(c) Ferromagnetic
(d) Paramagnetic
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60. A metal that is difficult to magnetise is said to have:
(a) High permeability
(b) Low permeability
(c) High reluctance
(d) Low retentivity
61. Which residual field is most difficult to demagnetise?
(a) Longitudinal
(b) Circular
(c) Vector
(d) Binodal
62. Which brings out surface indications most clearly?
(a) AC
(b) DC
(c) Pulsed DC
(d) DC with surge
63. To detect lengthwise defects on the inside diameter of hollow parts, you should:
(a) Pass current through it
(b) Magnetise with a coil
(c) Pass current through a central conductor
(d) Increase the amperage used
64. Which of the following is most often used for dry magnetic particle inspection:
(a) Full cycle direct current
(b) Half wave rectified alternating current
(c) High voltage, low amperage current
(d) Direct current from electrolytic cells
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65. When a magnetic field is induced in a part with prods spaced 150mm apart, the field
is:
(a) Solenoidal
(b) Circular
(c) Longitudinal
(d) Distorted trapezoidal
66. With current flowing from + to - in a coil, a longitudinal field is created. Which of the
following may be used to establish the direction of the magnetic field?
(a) Left hand rule
(b) Right hand rule
(c) Ohms law
(d) There is no relevant law
67. Which form of magnetisation is easiest to control in most parts?
(a) Longitudinal magnetisation
(b) Permanent magnetism
(c) Circular magnetization
(d) Parallel magnetization
68. The strength of a magnetic field within a coil is determined by:
(a) The current in the coil
(b) The number of turns in the coil\
(c) The diameter of the coil
(d) All of the above factors
69. The field in a section of pipe being magnetised by means of a central conductor is
stronger at:
(a) The ends of the pipe
(b) The outer surface of the pipe
(c) The inside surface of the pipe
(d) The middle of the pipe wall
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70. The space within and surrounding a magnetized part of a conductor carrying a current
is known as:
(a) Saturation point
(b) Magnetic field
(c) Ferromagnetic
(d) Paramagnetic
71. Subjecting the part to a magnetic field that is constantly reversing in polarity and
gradually diminishing in strength accomplishes which of the following:
(a) Magnetises the part
(b) Removes residual field from the part
(c) Soaks in the flux density
(d) Helps find deep lying defects
72. The type of method most frequently used with mobile equipment is the:
(a) Indirect induction method
(b) Wet method with auxiliary tank
(c) Yoke method
(d) Dry magnetic particle powder method
73. Which of the following is NOT a liquid vehicle in which particles are suspended in
magnetic particle testing:
(a) Water treated with a wetting agent
(b) Kerosene
(c) Gasoline
(d) Water treated with antifoam
74. The most common cause of non relevant indications in MT is:
(a) Over magnetisation
(b) Low amperage
(c) High flux density
(d) Under magnetisation
75. When a ferromagnetic material is in an unmagnetized state, the domains are:
(a) Aligned in a North and South direction
(b) Aligned in an East West direction
(c) Randomly organized
(d) Balanced to produce a gauss rating of 2
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76. Paramagnetic materials:
(a) Are commonly inspected using magnetic particle testing
(b) Are affected by magnetic fields
(c) Cannot be magnetized
(d) Have low reluctance to establishment of magnetic flux
77. What type of magnetization uses the formula:
I = 45000/(L/D)N where I is the current in Amperes, N the number of turns of the
magnetizing coil, L the length of the cylindrical test piece and D its diameter.
(a) Circular
(b) Longitudinal
(c) Swinging field
(d) Central conductor
78. The magnetic field is the strongest when:
(a) The magnetising current is flowing
(b) The magnetising voltage is applied
(c) The leakage field is flowing
(d) The magnetising current is off
79. The retentivity of a material describes:
(a) The length of time required to demagnetise it
(b) The depth of the magnetic field in the part
(c) The ability to retain the magnetic field
(d) The ease with which it can be demagnetized
80. A material with a wider hysteresis loop has:
(a) Lower reluctance
(b) Lower residual magnetism
(c) Higher residual magnetism
(d) Higher permeability
81. The unit usually used to denote flux density is the:
(a) Henry
(b) Angstrom
(c) Gauss
(d) Ampere
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82. Which technique is the most sensitive?
(a) Residual
(b) Continuous
(c) Permanent
(d) Interrupted
83. An electric current through a copper wire:
(a) Creates a magnetic field around the wire
(b) Creates magnetic poles in the wire
(c) Magnetises the wire
(d) Does not create a magnetic field
84. What rule describes the direction of current flow (+ to -) when lines of magnetic force
surround a conductor?
(a) Left hand rule
(b) Right hand rule
(c) Flux density rule
(d) Reluctance rule
85. The areas on a magnetised part from which the magnetic field is leaving or returning
into the part are called:
(a) Salient points
(b) Defects
(c) Magnetic poles
(d) Nodes
86. The opposition that a ferromagnetic material shows to the establishment of a magnetic
field is called:
(a) Retentivity
(b) Reluctance
(c) Coercive force
(d) Permeability
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87. The magnetism which remains in a piece of magnetisable material after the
magnetising force has been removed is called the:
(a) Tramp field
(b) Residual field
(c) Damped field
(d) Permanent field
88. A material with a narrower hysteresis loop has:
(a) Higher permeability
(b) Lower retentivity
(c) Lower coercive force
(d) All of the above
89. The correct number of ampere-turns for a given test specimen is determined by:
(a) Its length
(b) The material and its diameter
(c) Both the length and the material
(d) Its diameter and length
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