Eddy Current Practise

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  • 1/92 Questions

    A term to define the phenomenon where, at very high frequencies, the eddy current flow is resrticted to an extremely thin outer layer of the conductor is:

    • Skin effect
    • High frequency filtration
    • Low frequency filtration
    • Any of these answers
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About This Quiz

Theory and application of non destructive testing method eddy current

Engineering Quizzes & Trivia

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  • 2. 

    Eddy current testing relies on the principle of:

    • Magnetostriction

    • Electromagnetic induction

    • Piezoelectric energy conversion

    • Magnetomotive force

    Correct Answer
    A. Electromagnetic induction
  • 3. 

    A term used to define 2 or more coils electrically connected in opposition such that any electromagentic condition which is not common to both a test specimen and areference specimen will produce an unbalance in the system is:

    • Differential

    • Absolute

    • Laminar

    • Flying probes

    Correct Answer
    A. Differential
  • 4. 

    The thickness of nonconductive coatings on a conductive base can be most simply measuredby:

    • Observing the lift-off effect caused by the coating

    • Testing both sides of the specimen

    • Varying the current in the test coil

    • Varying the test frequency over a given range during the test

    Correct Answer
    A. Observing the lift-off effect caused by the coating
  • 5. 

    The symbol commonly used to signify impedance is:

    • Z

    • X; E

    • R

    • Xc

    Correct Answer
    A. Z
  • 6. 

    The actual frequency used in any specific eddy current inspection should be selectedon the basis of the:

    • Thickness of the material

    • Desired depth of penetration

    • Degree of sensitivity or resolution required

    • Purpose of the inspection

    • All of these

    Correct Answer
    A. All of these
  • 7. 

    The conductivity value for a metal is a function of the :

    • Heat treatment given the metal

    • Cold working performed on the metal

    • Aging process used on the metal

    • All of the answers

    Correct Answer
    A. All of the answers
  • 8. 

    When testing by the eddy current method, discontinuities will be most easily detected when the eddy currents are:

    • Coplanar with the major plane of the discontinuity

    • Perpendicular to the major plane of the discontinuity

    • Parallel to the major plane of the discontinuity

    • 90 degress out of the phase with current in the coil

    Correct Answer
    A. Perpendicular to the major plane of the discontinuity
  • 9. 

    Tubing is generally inspected using:

    • U-Shaped coils

    • Gap coils

    • Encircling coils

    • None of the answers

    Correct Answer
    A. Encircling coils
  • 10. 

    The atoms of a metal showing magnetic characteristics are grouped into regions whichare the smallest known permanent magnets. These regions are called:

    • Lattice structures

    • Cells

    • Domains

    • Planetary spins

    Correct Answer
    A. Domains
  • 11. 

    When the voltage applied to a circuit and the current through the circuit both reach theirmaximums and minimums at the same time, the voltage and current are:

    • Additive

    • In phase

    • Regenerative

    • Out of phase

    Correct Answer
    A. In phase
  • 12. 

    When a rod is placed in an encircling type of coil, the density of eddy currents will be greatest:

    • At the surface

    • At the center

    • Midway between the surface and center

    • None of these

    Correct Answer
    A. At the surface
  • 13. 

    When testing small parts in an eddy current encircling coil for permeability measurements,which of the following test parameters may be considered important?

    • Length of the test sample

    • Thickness of the test sample

    • Cross-sectional area of the test sample

    • All  answers are correct

    Correct Answer
    A. All  answers are correct
  • 14. 

    When testing ferrous materials, a small but detectable portion of the magnetic flux in the material will pass outside the metal when a surface discontinuity is encountered. This flux iscalled:

    • Air flux

    • Leakage flux

    • Induced flux

    • None of these

    Correct Answer
    A. Leakage flux
  • 15. 

     A term used to describe the effect observed due to a change in the electromagnetic coupling between a test specimen and a probe coil when the distance of separation between themis varied is:

    • Fill factor

    • Edge effect

    • End effect

    • Lift off

    Correct Answer
    A. Lift off
  • 16. 

    The term used to define the value of H field required to decrease the remanence of a material to zero is:

    • Coercive force

    • Magnetizing force

    • Back emf

    • The overlap value

    Correct Answer
    A. Coercive force
  • 17. 

    The magnetizing force of an eddy current test coil is usually designated by the:

    • Symbol u

    • Symbol o

    • Letter--B

    • Letter--H

    Correct Answer
    A. Letter--H
  • 18. 

    When a nonmagnetic rod is placed inside an eddy current test coil:

    • The magnetic field generated by the coil is increased in intensity

    • The distribution of eddy currents is uniform through the rod's cross section

    • The distribution of eddy currents is at a maximum at the rod's surface, or near the surface,and decreases to essentially zero at the rod's center

    • The temperature of the rod decreases

    Correct Answer
    A. The distribution of eddy currents is at a maximum at the rod's surface, or near the surface,and decreases to essentially zero at the rod's center
  • 19. 

    The magnetic field generated by eddy currents induced in a test specimen:

    • Opposes the magnetic field that induced the eddy currents

    • Reinforces the magnetic field that induced the eddy currents

    • Cancels the magnetic field that induced the eddy currents

    • Has no effect on the magnetic field that induced the eddy currents

    Correct Answer
    A. Opposes the magnetic field that induced the eddy currents
  • 20. 

    The inductive reactance of a test coil can be calculated using the formula:

    • Xr = 2 pie L

    • Xr = 1/2 pie L

    • Xr = 2 pie fL

    • Xr = 1R

    Correct Answer
    A. Xr = 2 pie fL
  • 21. 

    The magnetic domains in an unmagnetized ferromagnetic material are:

    • Arranged to facilitate the condition of electrons

    • Randomly oriented and neutralize each other

    • Uniformly oriented

    • Create a major north and south pole in the material

    Correct Answer
    A. Randomly oriented and neutralize each other
  • 22. 

    The heating effect in magnetic materials caused by work required to rotate magneticdomains can be eliminated by:

    • Increasing the rate of displacement of the specimen through the coil

    • Magnetically saturating the test specimen

    • Decreasing the rate of displacement of the test specimen throughthe test coil

    • Testing in an air-conditioned room

    Correct Answer
    A. Magnetically saturating the test specimen
  • 23. 

    When eddy current testing a nonferrous material, the choice of test frequency is determinedby the :

    • Degree of phase discrimination required

    • Eddy current penetration needed

    • Rate of response required

    • All of these

    Correct Answer
    A. All of these
  • 24. 

    The inductive reactance of a coil is measured in units of:

    • Mhos

    • Ohms

    • Henry's

    • Gauss

    Correct Answer
    A. Ohms
  • 25. 

    When the electrical current in an eddy current coil reverses direction:

    • The direction of the eddy currents in a part remains the same

    • The eddy currents in the test part will change phase 45 degrees

    • The direction of the eddy currents in the part also reverses

    • The eddy currents in the part remain the same

    Correct Answer
    A. The direction of the eddy currents in the part also reverses
  • 26. 

    When a magnetic material is placed in a region of an applied magnetizing force(H), magnetic field (B) is developed in the material by means of:

    • Induction

    • Conduction

    • Heat transfer

    • Magnetic domain transfer

    Correct Answer
    A. Induction
  • 27. 

    A major problem associated with eddy current test method is the:

    • Inability of eddy current testing to accurately measure conductivity

    • Need to test at low speeds to prevent skipping

    • Large number of known or unknown variables which appear in the output indication

    • Inability of eddy current testing to detect small discontinuities

    Correct Answer
    A. Large number of known or unknown variables which appear in the output indication
  • 28. 

    Which of the following materials would have the highest resistivity value?

    • Aluminum with a 42% IACS rating

    • Magnesium with a 37% IACS rating

    • Cast steel with a 10.7% IACS rating

    • Zirconium with a 3.4% IACS rating

    Correct Answer
    A. Zirconium with a 3.4% IACS rating
  • 29. 

    The fill factor when a 1/2 inch diameter bar is inserted in a 1 inch diameter coil is:

    • 0.5 (50%)

    • 0.75 (75%)

    • 1.0 (100%)

    • 0.25 (25%)

    Correct Answer
    A. 0.25 (25%)
  • 30. 

    When the H field strength around a material is increased and then decreased to zero,the induction field B within the part does not return to zero, the term to define this Bvalue when H has returned to zero is:

    • Coercive force

    • Residual Magnetism

    • Saturation value

    • Hysteresis loss

    Correct Answer
    A. Residual Magnetism
  • 31. 

    The 3 major specimen parameters which influence eddy current testing are:

    • Electrical conductivity, frequency, and material geometry

    • Density, permeability, and frequency

    • Electrical conductivity, permeability, and material geometry

    • Thermal conductivity, electrical conductivity, and permeability

    Correct Answer
    A. Electrical conductivity, permeability, and material geometry
  • 32. 

    Frequency ratio f/f can be defined as:

    • The argument of the mathematical function describing the electromagnetic field within the test specimen

    • Test frequency divided by limit frequency

    • Neither

    • Both

    Correct Answer
    A. Test frequency divided by limit frequency
  • 33. 

    In eddy current testing, the specimen is coupled to the test coil by:

    • Core coupling

    • Magnetic saturation

    • The coil's magnetic field

    • Magnetic domains

    Correct Answer
    A. The coil's magnetic field
  • 34. 

    A term used to define the timing relationship invovled in alternating current signals is:

    • Magnitude

    • Phase

    • Impedance

    • Reactance

    Correct Answer
    A. Phase
  • 35. 

    Which of the following could be used to suppress unwanted high frequency harmonics?

    • Low pass filter

    • Oscillator

    • Phase discriminator

    • High pass filter

    Correct Answer
    A. Low pass filter
  • 36. 

    The impedance of a test coil usually can be represented by the vector sum of:

    • Inductive reactance and resistance

    • Capacitive reactance and resistance

    • Inductive reactance and capacitive reactance

    • Inductance and capacitance

    Correct Answer
    A. Inductive reactance and resistance
  • 37. 

    A method of minimizing the effect of indications caused by gradual dimensional changes whileretaining the indications caused by discontinuities is to:

    • Include a high pass filter in the eddy current test equipment

    • Include a low pass filter in the eddy current test equipment

    • Increase the band pass of the amplifier

    • Use the impedance method of testing

    Correct Answer
    A. Include a high pass filter in the eddy current test equipment
  • 38. 

    Which of the following methods may be used to improve the signal-to-noise ratio of an eddycurrent test system?

    • Filtering or differentiation

    • Phase discrimination

    • Intergration

    • All 3 are correct

    Correct Answer
    A. All 3 are correct
  • 39. 

    In a test coil consisting of both a primary and secondary winding, the voltage across thesecondary is a function of:

    • Test material permeability

    • Test frequency

    • Geometry of the test object

    • All answers are correct

    Correct Answer
    A. All answers are correct
  • 40. 

    At a fixed test frequency, in which of the following materials will the eddy currentpenetration be greatest?

    • Aluminum (35% IACS conductivity)

    • Brass (15% IACS conductivity)

    • Copper (95% IACS conductivity)

    • Lead (7% IACS conductivity)

    Correct Answer
    A. Lead (7% IACS conductivity)
  • 41. 

    Which of the following conditions is not important when selecting specimens to be usedas reference standards?

    • The specimen should be of the same size and shape as the piece to be tested

    • The specimen should have the same heat treatment as the piece to be tested

    • The surface finish of the specimen should be the same as the piece to be tested

    • If the material is aluminum, the surface should be anodized

    Correct Answer
    A. If the material is aluminum, the surface should be anodized
  • 42. 

    An out-of-phase condition between current and voltage:

    • Can exist only in the primary winding of an eddy current coil

    • Can exist only in the secondary winding of an eddy current coil

    • Can exist in both the primary and secondary windings of an eddy current coil

    • Exist only in the test specimen

    Correct Answer
    A. Can exist in both the primary and secondary windings of an eddy current coil
  • 43. 

    For age hardenable aluminum and titanium alloys, changes in hardness are indicated bychanges in:

    • Rententivity

    • Permeability

    • Conductivity

    • Magnetostriction

    Correct Answer
    A. Conductivity
  • 44. 

     term fill factor applies to:

    • A surface coil

    • Coaxial cable

    • A encircling coil

    • All of these

    Correct Answer
    A. A encircling coil
  • 45. 

    2 TEST COILS ARE OFTEN USED IN A BRIDGE CIRCUIT

    • Eliminate skin effect

    • Determine the differences between a known standard sample

    • Increase the conductivity of the circuit

    • Decreases the system sensitivity

    Correct Answer
    A. Determine the differences between a known standard sample
  • 46. 

    Which of the following would be easier to detect in tubing by the eddy currentmethod using self comparison differential coil arrangement?

    • Gradual changes in diameter

    • Gradual changes in conductivity

    • Changes in temperature

    • Short flaws

    Correct Answer
    A. Short flaws
  • 47. 

    Which of the following materials would be more likely used as a mounting material for a probecoil?

    • Aluminum

    • Fiberglass

    • Copper

    • Steel

    Correct Answer
    A. Fiberglass
  • 48. 

    Doubling the number of turns on a coil will:

    • Double the inductance

    • Halve the inductance

    • Decrease the inductance by a factor of 4

    • Increase the inductance by a factor of 4

    Correct Answer
    A. Increase the inductance by a factor of 4
  • 49. 

    When testing tubing, using an encircling (OD) coil, What is the phase relationship of the output signals from identical ID and OD discontinuities?

    • The signals are in phase

    • The phase of the OD discontinuity leads the phase of the ID discontinuity

    • The phase of the OD discontinuity lags the phase of the ID discontinuity

    • Indeterminate

    Correct Answer
    A. The phase of the OD discontinuity leads the phase of the ID discontinuity

Quiz Review Timeline (Updated): Mar 22, 2022 +

Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

  • Current Version
  • Mar 22, 2022
    Quiz Edited by
    ProProfs Editorial Team
  • Apr 06, 2010
    Quiz Created by
    Ndtputz
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