Eddy Current Testing Technician
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
1. What is the primary physical principle used in eddy current testing?
A. Magnetostriction
B. Electromagnetic induction
C. Ultrasonic reflection
D. Thermal expansion
Answer: Electromagnetic induction
Rationale: Eddy current testing uses electromagnetic induction to generate
circulating electrical currents in conductive materials and detect changes caused
by discontinuities or material variations.
2. Which type of material can generally be inspected using conventional eddy
current testing?
A. Wood
B. Glass
C. Electrically conductive materials
D. Rubber
Answer: Electrically conductive materials
Rationale: Eddy currents require an electrically conductive material because they
are induced by a changing electromagnetic field.
, 3. What device is commonly used to generate the alternating magnetic field in
eddy current testing?
A. Probe coil
B. Thermocouple
C. Photodiode
D. Radiation detector
Answer: Probe coil
Rationale: An energized probe coil produces an alternating magnetic field that
induces eddy currents in the conductive test material.
4. What happens to the impedance of a probe coil when it is coupled to a
conductive test specimen?
A. It may change in magnitude and phase
B. It always becomes zero
C. It becomes purely resistive
D. It is unaffected
Answer: It may change in magnitude and phase
Rationale: The specimen's conductivity, permeability, geometry, and
discontinuities influence the coil's impedance, producing measurable amplitude
and phase changes.
5. What is lift-off in eddy current testing?
A. The removal of the probe cable
B. The distance between the probe and test surface
C. The depth of a crack
D. The frequency of inspection
Answer: The distance between the probe and test surface
Rationale: Lift-off describes the spacing between the probe and the material
surface and can significantly affect the eddy current signal.
, 6. Which parameter primarily determines the depth of eddy current
penetration?
A. Frequency
B. Probe color
C. Cable length only
D. Display brightness
Answer: Frequency
Rationale: Lower frequencies generally provide greater penetration, while
higher frequencies concentrate eddy currents closer to the surface.
7. Increasing test frequency generally causes the effective penetration depth
to:
A. Increase
B. Decrease
C. Remain exactly the same
D. Become infinite
Answer: Decrease
Rationale: Higher frequencies produce stronger electromagnetic attenuation and
therefore shallower effective penetration.
8. What is skin effect?
A. A chemical reaction at the surface
B. Concentration of alternating current near the material surface
C. Mechanical hardening of the surface
D. A type of probe wear
Answer: Concentration of alternating current near the material surface
Rationale: Alternating currents tend to concentrate near the surface of
conductive materials, with current density decreasing with depth.
, 9. Which factor can strongly affect eddy current response in ferromagnetic
materials?
A. Magnetic permeability
B. Paint color
C. Ambient noise only
D. Surface temperature only
Answer: Magnetic permeability
Rationale: Changes in magnetic permeability can substantially influence
electromagnetic coupling and probe impedance, making ferromagnetic
inspection more complex.
10.What is a common advantage of eddy current testing?
A. It requires the material to be nonconductive
B. It can detect surface and near-surface discontinuities
C. It always measures defect depth exactly
D. It requires direct electrical contact
Answer: It can detect surface and near-surface discontinuities
Rationale: Eddy current testing is particularly effective for detecting surface and
near-surface cracks and other discontinuities in conductive materials.
11.Which probe configuration is commonly used for scanning relatively large
surface areas?
A. Pencil or surface probe
B. Large-area array or scanning probe
C. Thermocouple
D. Radiation source
Answer: Large-area array or scanning probe
Rationale: Scanning and array probes allow efficient coverage of larger surfaces
while maintaining appropriate sensitivity.
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
1. What is the primary physical principle used in eddy current testing?
A. Magnetostriction
B. Electromagnetic induction
C. Ultrasonic reflection
D. Thermal expansion
Answer: Electromagnetic induction
Rationale: Eddy current testing uses electromagnetic induction to generate
circulating electrical currents in conductive materials and detect changes caused
by discontinuities or material variations.
2. Which type of material can generally be inspected using conventional eddy
current testing?
A. Wood
B. Glass
C. Electrically conductive materials
D. Rubber
Answer: Electrically conductive materials
Rationale: Eddy currents require an electrically conductive material because they
are induced by a changing electromagnetic field.
, 3. What device is commonly used to generate the alternating magnetic field in
eddy current testing?
A. Probe coil
B. Thermocouple
C. Photodiode
D. Radiation detector
Answer: Probe coil
Rationale: An energized probe coil produces an alternating magnetic field that
induces eddy currents in the conductive test material.
4. What happens to the impedance of a probe coil when it is coupled to a
conductive test specimen?
A. It may change in magnitude and phase
B. It always becomes zero
C. It becomes purely resistive
D. It is unaffected
Answer: It may change in magnitude and phase
Rationale: The specimen's conductivity, permeability, geometry, and
discontinuities influence the coil's impedance, producing measurable amplitude
and phase changes.
5. What is lift-off in eddy current testing?
A. The removal of the probe cable
B. The distance between the probe and test surface
C. The depth of a crack
D. The frequency of inspection
Answer: The distance between the probe and test surface
Rationale: Lift-off describes the spacing between the probe and the material
surface and can significantly affect the eddy current signal.
, 6. Which parameter primarily determines the depth of eddy current
penetration?
A. Frequency
B. Probe color
C. Cable length only
D. Display brightness
Answer: Frequency
Rationale: Lower frequencies generally provide greater penetration, while
higher frequencies concentrate eddy currents closer to the surface.
7. Increasing test frequency generally causes the effective penetration depth
to:
A. Increase
B. Decrease
C. Remain exactly the same
D. Become infinite
Answer: Decrease
Rationale: Higher frequencies produce stronger electromagnetic attenuation and
therefore shallower effective penetration.
8. What is skin effect?
A. A chemical reaction at the surface
B. Concentration of alternating current near the material surface
C. Mechanical hardening of the surface
D. A type of probe wear
Answer: Concentration of alternating current near the material surface
Rationale: Alternating currents tend to concentrate near the surface of
conductive materials, with current density decreasing with depth.
, 9. Which factor can strongly affect eddy current response in ferromagnetic
materials?
A. Magnetic permeability
B. Paint color
C. Ambient noise only
D. Surface temperature only
Answer: Magnetic permeability
Rationale: Changes in magnetic permeability can substantially influence
electromagnetic coupling and probe impedance, making ferromagnetic
inspection more complex.
10.What is a common advantage of eddy current testing?
A. It requires the material to be nonconductive
B. It can detect surface and near-surface discontinuities
C. It always measures defect depth exactly
D. It requires direct electrical contact
Answer: It can detect surface and near-surface discontinuities
Rationale: Eddy current testing is particularly effective for detecting surface and
near-surface cracks and other discontinuities in conductive materials.
11.Which probe configuration is commonly used for scanning relatively large
surface areas?
A. Pencil or surface probe
B. Large-area array or scanning probe
C. Thermocouple
D. Radiation source
Answer: Large-area array or scanning probe
Rationale: Scanning and array probes allow efficient coverage of larger surfaces
while maintaining appropriate sensitivity.
