Chapter: Magnetic Particle Testing Level 1
201.

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
Answer» A. Soft steels with high permeability
202.

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
Answer» C. Most reliable for finding surface cracks in all types of material
203.

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
Answer» D. The ability to detect discontinuities filled with foreign material
204.

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
Answer» C. Magnetic particle testing
205.

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
Answer» D. All of the above
206.

A discontinuity which is produced during solidification of the molten metal is called:

A. Inherent
B. Processing
C. Service
D. None of the above
Answer» A. Inherent
207.

Pipe would be classified as what type of discontinuity?

A. Inherent
B. Processing
C. Service
D. None of the above
Answer» A. Inherent
208.

A seam would be classified as what type of discontinuity?

A. Inherent
B. Processing
C. Service
D. None of the above
Answer» B. Processing
209.

A lamination in steel plate would be classified as what type of discontinuity?

A. Inherent
B. Processing
C. Service
D. None of the above
Answer» B. Processing
210.

An internal rupture caused by working steel at improper temperatures is called a:

A. Lap
B. Cold shut
C. Forging burst
D. Slag inclusion
Answer» C. Forging burst
211.

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
Answer» D. Fatigue cracks
212.

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
Answer» A. Stress corrosion cracks
213.

Which of the following are ferromagnetic materials?

A. Aluminium, iron, copper
B. Iron, copper, nickel
C. Copper, aluminium, silver
D. Iron, cobalt, nickel
Answer» D. Iron, cobalt, nickel
214.

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
Answer» B. Coercive force
215.

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
Answer» D. Poles
216.

The ease with which a magnetic field can be established in a test piece is called:

A. Reluctance
B. Retentivity
C. Permeability
D. Electromagnetism
Answer» C. Permeability
217.

Opposition to establishment of a magnetic field is called:

A. Reluctance
B. Retentivity
C. Permeability
D. Electromagnetism
Answer» A. Reluctance
218.

The ability of a material to remain magnetic after the magnetising force is removed is called:

A. Reluctance
B. Retentivity
C. Permeability
D. Electromagnetism
Answer» B. Retentivity
219.

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
Answer» C. Circular field
220.

Which of the following produces a circular field?

A. Coil
B. Head shot
C. Yoke
D. All of the above
Answer» B. Head shot
221.

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
Answer» B. A fast break technique
222.

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
Answer» C. 90 degrees
223.

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
Answer» A. Central conductor
224.

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
Answer» D. The centre of a bar magnetised with a head shot
225.

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
Answer» D. The inside surface of a ferromagnetic tube magnetised with a central conductor
226.

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
Answer» C. Preventing arc burns
227.

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
Answer» A. Parallel to a line connecting the prod contact points
228.

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
Answer» D. All of the above
229.

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
Answer» C. The DC magnetic fields are more penetrating
230.

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
Answer» D. A nonmagnetic conductor carrying a 50 Hz AC current
231.

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
Answer» B. Rectified AC
232.

Fields generated in ferromagnetic material with AC current are useful for locating:

A. All discontinuities
B. Surface cracks
C. Subsurface discontinuities
D. Internal porosity
Answer» B. Surface cracks
233.

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
Answer» B. 1000 ampere turns/25mm of diameter
234.

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
Answer» D. Coil magnetisation
235.

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
Answer» A. The test piece is not larger than 1/10 the cross sectional area of the coil
236.

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
Answer» C. At 90 degrees
237.

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
Answer» A. Parallel
238.

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
Answer» B. One half
239.

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
Answer» A. Twice
240.

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
Answer» B. In a linear manner
241.

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
Answer» B. Same
242.

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
Answer» C. Zero
243.

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
Answer» B. Same
244.

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
Answer» D. Mixture of elongated and globular
245.

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
Answer» B. Dry
246.

Which of the following colours is readily available for magnetic particle test powder?

A. Red
B. Gray
C. Black
D. All of the above
Answer» D. All of the above
247.

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
Answer» C. Residual method
248.

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
Answer» A. High rententivity
249.

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
Answer» B. Fine surface cracks
250.

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
Answer» C. Obtaining maximum contrast with the test piece background
251.

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
Answer» A. Surface discontinuities only
252.

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
Answer» C. Continuous field, wet method
253.

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
Answer» B. The magnetic field, as shown by a hysteresis curve, is less when there is no magnetising force
254.

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
Answer» D. None of the above is true
255.

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
Answer» B. Superior sensitivity for fine surface cracks
256.

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
Answer» A. Good sensitivity for subsurface discontinuities
257.

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
Answer» B. Loss of sensitivity to finer discontinuities
258.

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
Answer» D. Excellent detection of completely subsurface discontinuities
259.

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
Answer» B. Ease of bath recovery and re-use
260.

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
Answer» B. Bath flammability hazards are eliminated
261.

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
Answer» A. Darkened area and black light are required
262.

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
Answer» C. Eye fatigue
263.

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
Answer» C. Eyeball fluorescence
264.

Which of the following represents ultraviolet light of wavelengths which are potentially injurious (1 Å = 10-10m)

A. 2000 to 3200Å
B. 3200 to 4000 Å
C. 4000 to 4600Å
D. 4600 to 5200 Å
Answer» A. 2000 to 3200Å
265.

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
Answer» D. Fluorescent
266.

Most fluorescent dyes used for magnetic particle testing fluoresce what colour?

A. Blue green
B. Yellow green
C. Blue black
D. Red orange
Answer» B. Yellow green
267.

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
Answer» A. The mercury vapour lamp
268.

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
Answer» D. All of the above
269.

The temperature above which steels become nonmagnetic is called the:

A. Zero retentivity
B. Curie point
C. Demagnetisation temperature
D. Random polar point
Answer» B. Curie point
270.

The temperature above which most soft steels become nonmagnetic is about:

A. 440ºC(770oF)
B. 523ºC (975ºF)
C. 626ºC (1160ºF)
D. 754ºC (1390ºF)
Answer» D. 754ºC (1390ºF)
271.

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
Answer» C. Passing through an AC coil
272.

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
Answer» A. DC is more penetrating
273.

The type of discontinuity which magnetic particle testing most effectively locates is:

A. Slag inclusions
B. Magnetic writing
C. Porosity
D. Surface cracks
Answer» D. Surface cracks
274.

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
Answer» B. Magnetic writing
275.

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
Answer» D. Heat treating
276.

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
Answer» D. All of the above
277.

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
Answer» A. Prods
278.

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
Answer» C. Root indication
279.

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
Answer» C. Settling test
280.

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
Answer» D. Shake or dust the powder onto the test piece with minimum velocity
281.

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
Answer» C. AC makes the magnetic particles more mobile on the test surface
282.

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
Answer» B. 2
283.

Maximum practical prod spacing is about:

A. 100 mm
B. 200 mm
C. 300 mm
D. 450 mm
Answer» B. 200 mm
284.

Magnetic lines of flux which are parallel to a discontinuity produce:

A. Strong indications
B. Weak indications
C. No indications
D. Fuzzy indications
Answer» C. No indications
285.

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
Answer» C. The area directly between the poles
286.

A minimum of external poles are produced by what type of magnetisation?

A. Continuous
B. Residual
C. Circular
D. Longitudinal
Answer» C. Circular
287.

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
Answer» D. Portable magnetic particle unit
288.

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
Answer» A. Eyeball fluorescence
289.

Which of the following types of magnetic fields may be present without any external evidence?

A. Circular
B. Longitudinal
C. Secondary
D. Tertiary
Answer» A. Circular
290.

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
Answer» B. Bath flammability hazards are eliminated
291.

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
Answer» C. Settling test
292.

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
Answer» B. Machining may create external poles
293.

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
Answer» A. Parallel to a line connecting the prod contract points
294.

Maximum practical prod spacing for a 2000 amp unit is about:

A. 100 mm
B. 200 mm
C. 300 mm
D. 450 mm
Answer» B. 200 mm
295.

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
Answer» A. DC is more penetrating
296.

Fluorescent magnetic particle indications should be inspected under

A. Fluorescent light
B. Any light
C. Black light
D. Red light
Answer» C. Black light
297.

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
Answer» C. Stress corrosion cracking
298.

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
Answer» D. Surface cracks
299.

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
Answer» D. Re-heat treating
300.

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
Answer» D. All of the above
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