Magnetic lines of force are:

imaginary concepts for mapping magnetic fields

manifestations of the "string-theory"

In order to be detectable by magnetic particle testing, a flaw must:

produce a leakage field at the test surface

be no deeper than 1mm below the surface

A void in an otherwise homogenous magnetized material presents itself as a point magnetic dipole. This is the basis for:

magnetic particle flaw detection

The flux density of the magnetism induced by a coil can be controlled by varying:

the number of turns in the coil

The width of a magnetic particle indication:

is always wider than the actual flaw opening

is equal to the height of particle indication

is determined by the angle of repose

When the central conductor MPI method is used to inspect a ring shaped object, or short cylinder:

both inside and outside surface and subsurface flaws can be found if the wall thickness is not too great

only inside diameter surface flaws can be found

only outside diameter surface flaws can be found

none of the above, central conductors cannot be used for ring shaped objects

The best way to demagnetize a long tube would be:

reversing D.C. with a central conductor

pulsating A.C. with a central conductor

passing the tube through an A.C. coil

To reduce the discomfort of eye fatigue when performing fluorescent MPI you can:

take breaks at regular intervals

wear yellow-green tinted glasses (of the appropriate filtering ability)

Nonrelevant indications due to residual local poles interfere with magnetic particle testing. For a successful examination one should?

Demagnetize then remagnetize in the desired direction

Based on the domain theory, an unmagnetized part has domains that are:

aligned 90 degrees to the current flow

A Trivia Quiz On Magnetic Particle Testing!

Reviewed by Matt Balanda

Matt Balanda, BS (Aerospace Engineering) |

Science Teacher

Review Board Member

Matt Balanda, a Calvary Chapel Christian School leader with a Bachelor's in Aerospace Engineering and Mathematics, transitioned from Aerospace Engineering to Education with a Master's from California Baptist University. As the High School Vice-Principal and Physics teacher, he nurtures students' love of learning and faith, creating an enriching and transformational educational experience.

, BS (Aerospace Engineering)

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A Trivia Quiz On Magnetic Particle Testing! - Quiz

Magnets have been used for a long time as a way to check steel components on production lines using a specific measure. Below is a trivia quiz on magnetic particle testing designed to help you see how well you understand the method as a whole. How about you check it out and get to refresh your understanding. All the best!

Questions and Answers

1.

Magnetic lines of force are:
- A.
  
  Isolated mono-poles
- B.
  
  Elongated bi-poles
- C.
  
  Manifestations of the "string-theory"
- D.
  
  Imaginary concepts for mapping magnetic fields
Correct Answer
D. Imaginary concepts for mapping magnetic fields

Explanation
Magnetic lines of force are not physical entities but rather a conceptual tool used to visualize and map magnetic fields. They represent the direction and strength of the magnetic field at different points in space. These lines are imaginary and do not actually exist as physical lines. Instead, they provide a way to understand and describe the behavior of magnetic fields.

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5
2.

In a ferromagnetic material, a region where all the atomic moments are aligned parallel to each other is called a:
- A.
  
  Magnetic zone
- B.
  
  Confederation
- C.
  
  Domain
- D.
  
  Magnetic junta
Correct Answer
C. Domain

Explanation
In a ferromagnetic material, a region where all the atomic moments are aligned parallel to each other is called a domain. This term refers to a small region within the material where the magnetic moments of the atoms are aligned in the same direction, creating a strong magnetic field. These domains contribute to the overall magnetization of the material.

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2
3.

In order to be detectable by magnetic particle testing, a flaw must:
- A.
  
  Be surface breaking
- B.
  
  Be no deeper than 1mm below the surface
- C.
  
  Produce a leakage field at the test surface
- D.
  
  All of the above
Correct Answer
C. Produce a leakage field at the test surface

Explanation
A flaw must produce a leakage field at the test surface in order to be detectable by magnetic particle testing. This means that the flaw must generate a magnetic field that can be detected by the testing equipment. Flaws that are surface breaking and no deeper than 1mm below the surface are more likely to produce a leakage field that can be detected. Therefore, the correct answer is that the flaw must produce a leakage field at the test surface.

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1
4.

A void in an otherwise homogenous magnetized material presents itself as a point magnetic dipole. This is the basis for:
- A.
  
  Magnetic particle flaw detection
- B.
  
  Multi frequency eddy current
- C.
  
  Para-magnetism
- D.
  
  De-magnetization
Correct Answer
A. Magnetic particle flaw detection

Explanation
When a void, or defect, is present in a magnetized material, it disrupts the homogeneity of the magnetic field and creates a point magnetic dipole. This means that the magnetic field is concentrated at the location of the void. Magnetic particle flaw detection takes advantage of this by using magnetic particles that are attracted to and accumulate around the void, making it visible and detectable. This technique is commonly used in industries such as manufacturing and engineering to identify defects or flaws in materials.

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1
5.

The point at which the magnetism in a material cannot be increased even though the magnetizing force continues to increase is known as the:
- A.
  
  Salient pole.
- B.
  
  Saturation point.
- C.
  
  Residual point.
- D.
  
  Remnant point.
Correct Answer
B. Saturation point.

Explanation
The saturation point is the point at which the magnetism in a material cannot be increased even though the magnetizing force continues to increase. At this point, the material is fully magnetized and any additional increase in the magnetizing force will not result in a further increase in magnetism.

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6.

The opposition to the formation of a magnetic flux in a magnetic circuit is referred to as:
- A.
  
  Reactance
- B.
  
  Reluctance
- C.
  
  Resistance
- D.
  
  Antimagnetics
Correct Answer
B. Reluctance

Explanation
Reluctance is the opposition to the formation of a magnetic flux in a magnetic circuit. It is similar to resistance in an electrical circuit, where it hinders the flow of current. Reluctance depends on the material properties and geometry of the magnetic circuit. It is measured in units of ampere-turns per weber (A-turns/Wb). Reactance, on the other hand, refers to the opposition to the flow of alternating current in an electrical circuit due to inductance or capacitance. Resistance is the opposition to the flow of direct current in an electrical circuit. Antimagnetics is not a recognized term in the context of magnetic circuits.

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1
7.

Hysteresis loops and the magnetic properties of materials may be affected by:
- A.
  
  Grain size
- B.
  
  Microstructure
- C.
  
  Chemical composition
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
Hysteresis loops and magnetic properties of materials can be influenced by various factors including grain size, microstructure, and chemical composition. Grain size refers to the size of individual crystals in a material, and it can affect the movement of magnetic domains within the material. Microstructure refers to the arrangement and distribution of different phases or constituents in a material, and it can impact the magnetic behavior. Chemical composition refers to the elements and their proportions present in a material, which can alter its magnetic properties. Therefore, all of these factors can have an impact on hysteresis loops and magnetic properties.

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1
8.

The value of H applied to bring the residual value of B to zero is called:
- A.
  
  Saturation field
- B.
  
  Demagnetization value
- C.
  
  Coercive force
- D.
  
  Phase reversal factor
Correct Answer
C. Coercive force

Explanation
The coercive force refers to the amount of magnetic field strength required to reduce the residual magnetism in a material to zero. It is the measure of a material's ability to resist demagnetization. In this context, when the value of H (magnetic field strength) is applied to bring the residual value of B (magnetic induction) to zero, it is referred to as the coercive force.

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9.

Of the following discontinuity categories, which one is considered most detrimental to the service life of an item?
- A.
  
  Subsurface inclusions
- B.
  
  Subsurface porosity and voids
- C.
  
  Cracks open to the surface
- D.
  
  All of the above
Correct Answer
C. Cracks open to the surface

Explanation
Cracks that are open to the surface are considered the most detrimental to the service life of an item because they provide direct pathways for external elements such as moisture, chemicals, and contaminants to penetrate into the material. This can lead to accelerated corrosion, degradation, and structural failure, significantly reducing the lifespan of the item. Subsurface inclusions and porosity may also affect the integrity of the material, but they do not directly expose the material to external factors like cracks open to the surface do.

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2
10.

The flux density of the magnetism induced by a coil can be controlled by varying:
- A.
  
  The coil size
- B.
  
  The current in the coil
- C.
  
  The number of turns in the coil
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
The flux density of the magnetism induced by a coil can be controlled by varying the coil size, the current in the coil, and the number of turns in the coil. The size of the coil affects the amount of magnetic field generated, with a larger coil producing a stronger field. The current flowing through the coil also influences the strength of the magnetic field, as a higher current results in a stronger field. Additionally, increasing the number of turns in the coil increases the magnetic field strength. Therefore, all of the above factors can be adjusted to control the flux density of the magnetism induced by a coil.

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1
11.

An electric current which flows steadily in one direction is:
- A.
  
  Direct current
- B.
  
  Full wave current
- C.
  
  Half wave current
- D.
  
  Alternating current
Correct Answer
A. Direct current

Explanation
Direct current refers to an electric current that flows consistently in one direction. Unlike alternating current, which periodically changes direction, direct current maintains a constant flow of electrons. This type of current is commonly used in batteries, electronic devices, and certain power systems where a steady flow of electricity is required.

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8
12.

A magnetic particle build-up from a discontinuity is strongest when the discontinuity is oriented:
- A.
  
  180° to the magnetic field.
- B.
  
  45° to the magnetic field.
- C.
  
  90° to the magnetic field.
- D.
  
  90° to the current flow.
Correct Answer
C. 90° to the magnetic field.

Explanation
When a discontinuity is oriented 90 degrees to the magnetic field, it creates a stronger magnetic particle build-up. This is because the magnetic field lines are perpendicular to the discontinuity, resulting in a greater concentration of magnetic particles at the discontinuity. When the discontinuity is oriented at other angles, the magnetic field lines and the discontinuity are not perpendicular, leading to a weaker magnetic particle build-up. Therefore, the strongest magnetic particle build-up occurs when the discontinuity is oriented 90 degrees to the magnetic field.

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6
13.

The most important characteristic(s) that a dry powder should have is/are:
- A.
  
  Low coercive force
- B.
  
  Low magnetic retentivity
- C.
  
  High magnetic permeability
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
A dry powder should have low coercive force, low magnetic retentivity, and high magnetic permeability. Low coercive force means that the powder can be easily magnetized and demagnetized. Low magnetic retentivity ensures that the powder does not retain a magnetic field after being magnetized. High magnetic permeability allows the powder to efficiently conduct magnetic flux. Therefore, all of these characteristics are important for a dry powder to effectively function in magnetic applications.

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5
14.

The negative magnetizing force required to reduce the residual flux density in a part to zero after saturation is called:
- A.
  
  Residual force
- B.
  
  Coercive force
- C.
  
  Demagnetizing field strength
- D.
  
  Null force
Correct Answer
B. Coercive force

Explanation
The coercive force is the negative magnetizing force required to reduce the residual flux density in a part to zero after saturation. This force is necessary to demagnetize the material and bring it back to its original state. It is called "coercive" because it represents the ability of a material to resist changes in its magnetic state. The coercive force is an important parameter in understanding the magnetic properties of a material and is often used in the design and analysis of magnetic devices.

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2
15.

In the inspection of a part, the following may justify rejection of some parts:
- A.
  
  Inherent defects
- B.
  
  Service defects
- C.
  
  Processing defects
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
All of the above may justify the rejection of some parts in the inspection of a part. Inherent defects refer to flaws or imperfections that are present in the part from the beginning, such as structural weaknesses or material defects. Service defects are defects that occur during the part's use or service, such as wear and tear or damage caused by external factors. Processing defects are defects that occur during the manufacturing or processing of the part, such as errors in production or assembly. Therefore, any of these defects can be valid reasons for rejecting parts during inspection.

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4
16.

The strength of a circular magnetic field is not determined by the ________ of a part:
- A.
  
  Permeability
- B.
  
  Diameter
- C.
  
  Length
- D.
  
  Any of the above
Correct Answer
C. Length

Explanation
The strength of a circular magnetic field is not determined by the length of a part. The strength of a magnetic field is determined by factors such as the permeability of the material and the diameter of the part. The length of the part does not have a direct impact on the strength of the magnetic field.

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17.

The width of a magnetic particle indication:
- A.
  
  Indicates flaw depth
- B.
  
  Is always wider than the actual flaw opening
- C.
  
  Is equal to the height of particle indication
- D.
  
  Is determined by the angle of repose
Correct Answer
B. Is always wider than the actual flaw opening

Explanation
The width of a magnetic particle indication is always wider than the actual flaw opening. This means that the indication of a flaw on a magnetic particle inspection will appear larger than the actual size of the flaw. This is because the magnetic particles tend to spread out and form a wider indication due to various factors such as the magnetic field, the type of particles used, and the surface tension of the liquid suspension. Therefore, it is important for inspectors to consider this when interpreting the indications and determining the severity of the flaws.

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2
18.

When the central conductor MPI method is used to inspect a ring shaped object, or short cylinder:
- A.
  
  Only inside diameter surface flaws can be found
- B.
  
  Only outside diameter surface flaws can be found
- C.
  
  Both inside and outside surface and subsurface flaws can be found if the wall thickness is not too great
- D.
  
  None of the above, central conductors cannot be used for ring shaped objects
Correct Answer
C. Both inside and outside surface and subsurface flaws can be found if the wall thickness is not too great

Explanation
The central conductor MPI method is capable of detecting both inside and outside surface flaws as well as subsurface flaws in a ring-shaped object or short cylinder, as long as the wall thickness is not too great. This method involves passing an electric current through the central conductor, creating a magnetic field that can reveal any flaws or defects in the material. The magnetic field interacts differently with different types of flaws, allowing for their detection. Therefore, this method is effective in identifying various types of flaws in ring-shaped objects.

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1
19.

Given a steel bar 1 foot long and 3 inches diameter, what current should you use for the coil shot with a 3 turn coil (part placed at bottom of coil)?
- A.
  
  100 amps
- B.
  
  2000 amps
- C.
  
  4000 amps
- D.
  
  None of the above
Correct Answer
D. None of the above
20.

When welds are required to have only partial penetration, use of HWDC yokes often give rise to nonrelevant indications. This problem can be eliminated by:
- A.
  
  Using an A.C. yoke
- B.
  
  Increasing leg spacing
- C.
  
  Reducing magnetizing current
- D.
  
  Using a pie gage
Correct Answer
A. Using an A.C. yoke

Explanation
When welds are required to have only partial penetration, the use of HWDC (Half Wave Direct Current) yokes can often result in nonrelevant indications. This means that the yoke may detect flaws or indications that are not actually relevant or significant to the weld being inspected. To eliminate this problem, it is recommended to use an A.C. (Alternating Current) yoke instead.

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1
21.

The best way to demagnetize a long tube would be:
- A.
  
  Reversing D.C. with a central conductor
- B.
  
  Pulsating A.C. with a central conductor
- C.
  
  A portable yoke
- D.
  
  Passing the tube through an A.C. coil
Correct Answer
A. Reversing D.C. with a central conductor

Explanation
Reversing DC with a central conductor is the best way to demagnetize a long tube because it involves reversing the direction of the current flow through the tube. This helps to neutralize any residual magnetism that may be present in the tube, effectively demagnetizing it. Pulsating AC with a central conductor may also be effective, but reversing DC is generally considered more reliable for demagnetization. Using a portable yoke or passing the tube through an AC coil may not provide the necessary reversed current flow to demagnetize the tube effectively.

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1
22.

To reduce the discomfort of eye fatigue when performing fluorescent MPI you can:
- A.
  
  Take breaks at regular intervals
- B.
  
  Wear yellow-green tinted glasses (of the appropriate filtering ability)
- C.
  
  Both a and b
- D.
  
  Increase dark adaption time
Correct Answer
C. Both a and b

Explanation
Taking breaks at regular intervals and wearing yellow-green tinted glasses (of the appropriate filtering ability) can both help reduce the discomfort of eye fatigue when performing fluorescent MPI. By taking breaks, the eyes are given a chance to rest and recover, reducing strain and fatigue. Wearing yellow-green tinted glasses can help filter out certain wavelengths of light that can cause eye strain and fatigue. Therefore, both options can be effective in reducing eye fatigue during fluorescent MPI.

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23.

Nonrelevant indications due to residual local poles interfere with magnetic particle testing. For a successful examination one should?
- A.
  
  Magnetize in another direction
- B.
  
  Demagnetize then remagnetize in the desired direction
- C.
  
  Use lower amperage
- D.
  
  Use more amperage
Correct Answer
B. Demagnetize then remagnetize in the desired direction

Explanation
Residual local poles can cause nonrelevant indications during magnetic particle testing. To overcome this interference, it is necessary to demagnetize the object first to remove any residual magnetism. After demagnetization, the object should be remagnetized in the desired direction to ensure a successful examination.

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24.

If a discontinuity is shallow and broad like a scratch, the flux lines may stream-line below the discontinuity. This will result in:
- A.
  
  A false indication
- B.
  
  A non-relevant indication
- C.
  
  A sub surface indication
- D.
  
  A lack of indication
Correct Answer
D. A lack of indication

Explanation
If a discontinuity is shallow and broad like a scratch, the flux lines may stream-line below the discontinuity. This means that the magnetic particles used to detect the discontinuity will not be able to gather and indicate the presence of the flaw. Therefore, there will be a lack of indication for the shallow and broad discontinuity.

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25.

Based on the domain theory, an unmagnetized part has domains that are:
- A.
  
  Randomly oriented
- B.
  
  Aligned north to south
- C.
  
  Aligned east to west
- D.
  
  Aligned 90 degrees to the current flow
Correct Answer
A. Randomly oriented

Explanation
Based on the domain theory, an unmagnetized part has randomly oriented domains. This means that the magnetic domains within the part are not aligned in any specific direction. This lack of alignment results in the absence of a magnetic field or magnetization in the part.

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26.

The areas on a magnetized part from which the magnetic field is leaving and entering the part are called:
- A.
  
  Salient points
- B.
  
  Discontinuities
- C.
  
  Magnetic poles
- D.
  
  Nodes
Correct Answer
C. Magnetic poles

Explanation
The areas on a magnetized part where the magnetic field is leaving and entering the part are called magnetic poles. Magnetic poles are the regions where the magnetic field lines originate (north pole) or terminate (south pole). These poles are responsible for the attraction or repulsion between magnets and are essential in understanding the behavior of magnetic materials.

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27.

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 demagnetized it
- D.
  
  The ability to retain the magnetic field
Correct Answer
A. The ease with which it can be magnetized

Explanation
The permeability of a material refers to its ability to allow the passage of magnetic lines of force. It describes the ease with which the material can be magnetized, meaning how easily it can become magnetized when exposed to a magnetic field. A high permeability material can be easily magnetized, while a low permeability material resists magnetization. Therefore, the correct answer is "the ease with which it can be magnetized".

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2
28.

Materials that are weakly attracted magnetically are called:
- A.
  
  Paramagnetic
- B.
  
  Diamagnetic
- C.
  
  Ferromagnetic
- D.
  
  Nonmagnetic
Correct Answer
A. Paramagnetic

Explanation
Paramagnetic materials are weakly attracted to a magnetic field due to the presence of unpaired electrons in their atomic or molecular orbitals. These materials become magnetized in the presence of a magnetic field but lose their magnetism once the field is removed. Diamagnetic materials, on the other hand, are weakly repelled by a magnetic field and do not retain any magnetism. Ferromagnetic materials have a strong attraction to a magnetic field and can retain their magnetism even after the field is removed. Nonmagnetic materials do not have any attraction or repulsion towards a magnetic field. Therefore, the correct answer is paramagnetic.

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3
29.

A part is adaptable to magnetic particle testing if:
- A.
  
  It is attached to an electrostatic field
- B.
  
  The material is ferromagnetic
- C.
  
  The material is nonferrous
- D.
  
  The material is an electric conductor
Correct Answer
B. The material is ferromagnetic

Explanation
The correct answer is that the material is ferromagnetic. Ferromagnetic materials have the ability to become magnetized when exposed to a magnetic field, making them suitable for magnetic particle testing. This testing method involves applying a magnetic field to the material and then applying magnetic particles to the surface. If there are any defects or cracks in the material, the particles will be attracted to them, making them visible and allowing for inspection.

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2
30.

Of the four sources of magnetism, which one is most often used in magnetic particle testing?
- A.
  
  The Earth's field
- B.
  
  Permanent magnets
- C.
  
  Mechanically-induced magnetism
- D.
  
  Electrically-induced magnetism
Correct Answer
D. Electrically-induced magnetism

Explanation
Electrically-induced magnetism is the most often used source of magnetism in magnetic particle testing. This is because electrically-induced magnetism allows for greater control and manipulation of the magnetic field, making it easier to detect and analyze magnetic particles. Permanent magnets, mechanically-induced magnetism, and the Earth's field may also be used in certain cases, but electrically-induced magnetism is the preferred choice due to its versatility and reliability in magnetic particle testing.

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31.

The lines of magnetic flux within and surrounding a magnetized part or around a conductor carrying current is known as:
- A.
  
  Saturation lines
- B.
  
  Magnetic field
- C.
  
  Ferromagnetic rays
- D.
  
  Coercive lines
Correct Answer
B. Magnetic field

Explanation
The lines of magnetic flux within and surrounding a magnetized part or around a conductor carrying current are known as the magnetic field. The magnetic field is a region in which magnetic forces can be detected and is represented by the direction and strength of the magnetic lines of force. It is responsible for the attractive or repulsive forces between magnets and the interaction between magnets and electric currents.

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32.

The end of the magnet at which the lines are thought of as entering the bar is:
- A.
  
  The north pole
- B.
  
  The south pole
- C.
  
  Both north and south poles
- D.
  
  None of the above
Correct Answer
B. The south pole

Explanation
The end of the magnet where the lines are thought of as entering the bar is the south pole. This is because magnetic field lines always flow from the north pole to the south pole.

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33.

A curve is sometimes drawn to show graphically the relationship of the magnetizing force to the strength of the magnetic field produced in a material. This is known as the:
- A.
  
  Magnetic force curve
- B.
  
  Hysteresis curve
- C.
  
  Saturation curve
- D.
  
  Induction curve
Correct Answer
B. Hysteresis curve

Explanation
A hysteresis curve is a graphical representation that shows the relationship between the magnetizing force and the strength of the magnetic field produced in a material. It is called a hysteresis curve because it illustrates the phenomenon of hysteresis, which refers to the lagging of the magnetic field behind the magnetizing force. This curve is important in understanding the magnetic properties of materials and is commonly used in the study of magnetic materials and devices.

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34.

The magnitude of the residual magnetic field in a specimen is dependent on:
- A.
  
  The length to diameter ratio
- B.
  
  The strength of the applied magnetizing force
- C.
  
  The right hand rule
- D.
  
  The left hand rule
Correct Answer
B. The strength of the applied magnetizing force

Explanation
The magnitude of the residual magnetic field in a specimen is dependent on the strength of the applied magnetizing force. This means that the stronger the magnetizing force applied to the specimen, the greater the residual magnetic field will be. The length to diameter ratio, the right hand rule, and the left hand rule are not directly related to the magnitude of the residual magnetic field.

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2
35.

If a crack exists in a circular magnet, the attraction of magnetic particles to the crack is caused by the:
- A.
  
  Coercive force
- B.
  
  Leakage field
- C.
  
  Doppler effect
- D.
  
  High reluctance at the crack
Correct Answer
B. Leakage field

Explanation
The attraction of magnetic particles to a crack in a circular magnet is caused by the leakage field. When there is a crack in the magnet, the magnetic field lines tend to concentrate at the crack, creating a leakage field. This leakage field attracts magnetic particles towards the crack, allowing for the detection of the crack using magnetic particle inspection techniques.

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8
36.

Alternating current produces a magnetic field in a part that has a better sensitivity to detect:
- A.
  
  Surface discontinuities
- B.
  
  Subsurface discontinuities
- C.
  
  Surface and subsurface discontinuities
- D.
  
  None of the above
Correct Answer
A. Surface discontinuities

Explanation
Alternating current produces a magnetic field that is primarily confined to the surface of a material. This magnetic field is better suited for detecting surface discontinuities, such as cracks or defects on the surface of a material. Subsurface discontinuities, on the other hand, may require other testing methods, such as ultrasonic or radiographic testing, which can penetrate deeper into the material to detect flaws beneath the surface. Therefore, the correct answer is surface discontinuities.

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5
37.

How is half wave direct current created?
- A.
  
  By alternating applications of power
- B.
  
  By transforming alternating current
- C.
  
  By rectifying alternating current
- D.
  
  None of the above
Correct Answer
C. By rectifying alternating current

Explanation
Half wave direct current is created by rectifying alternating current. Rectification is the process of converting alternating current (AC) into direct current (DC) by allowing current to flow in only one direction. In the case of half wave rectification, only one half of the AC waveform is allowed to pass through, resulting in a pulsating DC waveform with current flowing in one direction.

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6
38.

What effect does the length of the part have in determining the correct amperage to induce a circular magnetic field?
- A.
  
  As the length increases, the amperage must increase
- B.
  
  As the length decreases, the amperage can be decreased
- C.
  
  The length does not have any effect on the required amperage
- D.
  
  The length is restricted to ensure a ratio between 2 and 15
Correct Answer
C. The length does not have any effect on the required amperage

Explanation
The length of the part does not have any effect on the required amperage. The correct amperage to induce a circular magnetic field is not dependent on the length of the part.

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3
39.

Circular magnetism can be induced in a material by:
- A.
  
  Headshot
- B.
  
  Prods
- C.
  
  Central conductor method
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
Circular magnetism can be induced in a material through various methods, including headshot, prods, and the central conductor method. These methods involve applying external forces or currents to the material, which results in the generation of a circular magnetic field. Therefore, the correct answer is "all of the above" as all the mentioned methods can induce circular magnetism in a material.

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1
40.

To ensure the inside of a hollow part is properly tested for lengthwise discontinuities, the part should be magnetized by:
- A.
  
  Passing current through the part
- B.
  
  Placing the part in a coil
- C.
  
  Passing current through a central conductor
- D.
  
  Any of the above would provide satisfactory results
Correct Answer
C. Passing current through a central conductor

Explanation
Passing current through a central conductor is the correct answer because this method allows for the magnetization of the entire hollow part, ensuring that all lengthwise discontinuities can be properly tested. By passing current through a central conductor, a magnetic field is generated that permeates the entire part, making it possible to detect any potential defects or discontinuities along its length. This method is effective in ensuring comprehensive testing of the hollow part for lengthwise defects.

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1
41.

Longitudinal magnetism is induced in a material by:
- A.
  
  Headshot
- B.
  
  Coil
- C.
  
  A yoke
- D.
  
  Both b and c
- E.
  
  All of the above
Correct Answer
D. Both b and c

Explanation
Longitudinal magnetism refers to the alignment of magnetic domains within a material along its length. This type of magnetism can be induced by both a coil and a yoke. A coil produces a magnetic field when an electric current flows through it, while a yoke is a magnetic circuit that helps to guide and concentrate the magnetic field. Therefore, both the coil and the yoke can contribute to the induction of longitudinal magnetism in a material. Hence, the correct answer is "both b and c" (coil and yoke).

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42.

What determines the correct ampere turns for inducing a longitudinal magnetic field in a part?
- A.
  
  The diameter and length of part
- B.
  
  The placement of the part in the coil
- C.
  
  The amount of fill factor between the part and coil
- D.
  
  All of the above are factors
Correct Answer
D. All of the above are factors

Explanation
The correct ampere turns for inducing a longitudinal magnetic field in a part are determined by all of the factors mentioned. The diameter and length of the part play a role in determining the strength of the magnetic field. The placement of the part in the coil also affects the magnetic field strength. Additionally, the amount of fill factor between the part and coil influences the magnetic field. Therefore, all of these factors need to be considered when determining the correct ampere turns for inducing a longitudinal magnetic field in a part.

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43.

Where is the strongest part of a magnetic field in a coil?
- A.
  
  Along the outside edge
- B.
  
  Along the inside surface
- C.
  
  In the center of the coil
- D.
  
  All of the above because the distribution must be equal
Correct Answer
B. Along the inside surface

Explanation
The strongest part of a magnetic field in a coil is along the inside surface. This is because the magnetic field lines are concentrated closer to the coil's core, resulting in a stronger field along the inside surface compared to the outside edge or the center of the coil.

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44.

The ampere turns for inducing a longitudinal field has been determined to be 15,000 ampere turns. If the stationary unit's coil has five windings, what amperage should the unit be set for to properly magnetize the part?
- A.
  
  3000 A
- B.
  
  5000 A
- C.
  
  7500 A
- D.
  
  15,000 A
Correct Answer
A. 3000 A

Explanation
The ampere turns for inducing a longitudinal field is determined to be 15,000 ampere turns. The stationary unit's coil has five windings. To properly magnetize the part, the amperage should be set for 3000 A.

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6
45.

When is it necessary to use D_effto calculate ampere turns?
- A.
  
  When there is a low fill factor
- B.
  
  When there is a high fill factor
- C.
  
  When the part is hollow
- D.
  
  At all times when calculating length to diameter ratios
Correct Answer
C. When the part is hollow

Explanation
When the part is hollow, it is necessary to use Deff to calculate ampere turns. This is because the effective length of the magnetic path is different for a hollow part compared to a solid part. Deff takes into account the cross-sectional area of the magnetic path and adjusts the length accordingly. Therefore, when calculating ampere turns for a hollow part, Deff is used to accurately determine the effective length of the magnetic path.

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2
46.

Which type of magnetic field produces a readily detectable north and south pole in a part?
- A.
  
  Circular
- B.
  
  Longitudinal
- C.
  
  Circular when a central conductor is used
- D.
  
  Circular when a headshot is used
Correct Answer
B. Longitudinal

Explanation
A longitudinal magnetic field produces a readily detectable north and south pole in a part. In a longitudinal magnetic field, the magnetic field lines run parallel to the direction of the current flow. This type of field can easily be detected using a compass or other magnetic field detection devices, as the north and south poles are clearly defined. Circular magnetic fields, on the other hand, do not have distinct north and south poles, making them less detectable. The options mentioning circular magnetic fields are therefore incorrect.

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3
47.

Magnetic flux lines that are parallel to a discontinuity produce:
- A.
  
  Strong indications
- B.
  
  Weak indications
- C.
  
  No indications
- D.
  
  Fuzzy indications
Correct Answer
C. No indications

Explanation
When magnetic flux lines are parallel to a discontinuity, they do not interact with the boundary and therefore do not produce any indications. This is because the flux lines are not crossing the boundary, resulting in no change in the magnetic field and no detection of the discontinuity.

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1
48.

What is a major consideration when selecting the particles to be used to perform a magnetic particle test?
- A.
  
  The particles must be very small
- B.
  
  The particles provide a high contrast to the surface of the test
- C.
  
  The particles must be able to absorb the vehicle to increase their mobility
- D.
  
  All of the above
Correct Answer
B. The particles provide a high contrast to the surface of the test

Explanation
When selecting particles to perform a magnetic particle test, a major consideration is that the particles provide a high contrast to the surface of the test. This is important because it allows for easier detection and visualization of any potential defects or cracks in the material being tested. By having particles that stand out against the surface, it becomes easier to identify any areas of concern and ensure the accuracy of the test results.

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1
49.

A key factor for selecting magnetic particles for MT is that they have:
- A.
  
  Good mobility
- B.
  
  High permeability
- C.
  
  Low retentivity
- D.
  
  All of the above factors to be an acceptable testing medium
Correct Answer
D. All of the above factors to be an acceptable testing medium

Explanation
For magnetic particle testing (MT), the particles used need to possess certain characteristics to effectively detect and indicate flaws or defects in materials. These characteristics include:
Good Mobility: Magnetic particles should be able to move freely and easily within the magnetic field, allowing them to be attracted to and accumulate at areas of magnetic flux leakage caused by defects.
High Permeability: Magnetic particles with high permeability are more responsive to magnetic fields, enhancing their ability to detect and indicate surface or near-surface defects in ferromagnetic materials.
Low Retentivity: Magnetic particles with low retentivity do not retain their magnetic properties after the magnetic field is removed. This property is important as it allows the particles to be easily removed from the surface after inspection, preventing interference with subsequent processes and ensuring a clear inspection area.
Therefore, all of the listed factors are important considerations when selecting magnetic particles for magnetic particle testing to ensure they provide reliable and accurate results.

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2
50.

When applying the magnetic bath during the continuous application method, when is the flow of the bath stopped?
- A.
  
  While the current is being applied
- B.
  
  Just before the current is applied to the part
- C.
  
  After the current has been applied to the part
- D.
  
  None of the above
Correct Answer
B. Just before the current is applied to the part

Explanation
In the continuous application method, the magnetic bath is applied while the current is being applied to the part. However, the flow of the bath is stopped just before the current is applied to the part. This is done to ensure that the part is properly prepared and ready to receive the current. By stopping the flow of the bath just before the current is applied, any excess bath is removed and the part is ready for the current to be applied.

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2

Matt Balanda |BS (Aerospace Engineering) |

Science Teacher

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Feb 10, 2019

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A Trivia Quiz On Magnetic Particle Testing!

Magnetic lines of force are:

In a ferromagnetic material, a region where all the atomic moments are aligned parallel to each other is called a:

In order to be detectable by magnetic particle testing, a flaw must:

A void in an otherwise homogenous magnetized material presents itself as a point magnetic dipole. This is the basis for:

The point at which the magnetism in a material cannot be increased even though the magnetizing force continues to increase is known as the:

The opposition to the formation of a magnetic flux in a magnetic circuit is referred to as:

Hysteresis loops and the magnetic properties of materials may be affected by:

The value of H applied to bring the residual value of B to zero is called:

Of the following discontinuity categories, which one is considered most detrimental to the service life of an item?

The flux density of the magnetism induced by a coil can be controlled by varying:

An electric current which flows steadily in one direction is:

A magnetic particle build-up from a discontinuity is strongest when the discontinuity is oriented:

The most important characteristic(s) that a dry powder should have is/are:

The negative magnetizing force required to reduce the residual flux density in a part to zero after saturation is called:

In the inspection of a part, the following may justify rejection of some parts:

The strength of a circular magnetic field is not determined by the ________ of a part:

The width of a magnetic particle indication:

When the central conductor MPI method is used to inspect a ring shaped object, or short cylinder:

Given a steel bar 1 foot long and 3 inches diameter, what current should you use for the coil shot with a 3 turn coil (part placed at bottom of coil)?

When welds are required to have only partial penetration, use of HWDC yokes often give rise to nonrelevant indications. This problem can be eliminated by:

The best way to demagnetize a long tube would be:

To reduce the discomfort of eye fatigue when performing fluorescent MPI you can:

Nonrelevant indications due to residual local poles interfere with magnetic particle testing. For a successful examination one should?

If a discontinuity is shallow and broad like a scratch, the flux lines may stream-line below the discontinuity. This will result in:

Based on the domain theory, an unmagnetized part has domains that are:

The areas on a magnetized part from which the magnetic field is leaving and entering the part are called:

The permeability of a material describes:

Materials that are weakly attracted magnetically are called:

A part is adaptable to magnetic particle testing if:

Of the four sources of magnetism, which one is most often used in magnetic particle testing?

The lines of magnetic flux within and surrounding a magnetized part or around a conductor carrying current is known as:

The end of the magnet at which the lines are thought of as entering the bar is:

A curve is sometimes drawn to show graphically the relationship of the magnetizing force to the strength of the magnetic field produced in a material. This is known as the:

The magnitude of the residual magnetic field in a specimen is dependent on:

If a crack exists in a circular magnet, the attraction of magnetic particles to the crack is caused by the:

Alternating current produces a magnetic field in a part that has a better sensitivity to detect:

How is half wave direct current created?

What effect does the length of the part have in determining the correct amperage to induce a circular magnetic field?

Circular magnetism can be induced in a material by:

To ensure the inside of a hollow part is properly tested for lengthwise discontinuities, the part should be magnetized by:

Longitudinal magnetism is induced in a material by:

What determines the correct ampere turns for inducing a longitudinal magnetic field in a part?

Where is the strongest part of a magnetic field in a coil?

The ampere turns for inducing a longitudinal field has been determined to be 15,000 ampere turns. If the stationary unit's coil has five windings, what amperage should the unit be set for to properly magnetize the part?

When is it necessary to use Deff to calculate ampere turns?

Which type of magnetic field produces a readily detectable north and south pole in a part?

Magnetic flux lines that are parallel to a discontinuity produce:

What is a major consideration when selecting the particles to be used to perform a magnetic particle test?

A key factor for selecting magnetic particles for MT is that they have:

When applying the magnetic bath during the continuous application method, when is the flow of the bath stopped?

When is it necessary to use D_effto calculate ampere turns?