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CGSB EDDY CURRENT TESTING (ET) LEVEL 2
QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) Q & A 2026 |INSTANT DOWNLOAD PDF
1. What is the basic principle of eddy current testing? A. Radiation absorption B. Electromagnetic induction C. Acoustic wave reflection D. Thermal conduction Rationale: Eddy current testing is based on electromagnetic induction where alternating current induces circulating currents in conductive materials. Correct Answer: B. Electromagnetic induction 2. Eddy currents are induced in a material that is: A. Magnetic only B. Conductive only C. Insulating D. Ceramic Rationale: Eddy currents require a conductive material to allow electron flow. Correct Answer: B. Conductive only
3. Which factor has the greatest effect on eddy current penetration depth? A. Color of material B. Frequency of excitation current C. Surface roughness only D. Operator skill Rationale: Higher frequency reduces penetration depth, while lower frequency increases it. Correct Answer: B. Frequency of excitation current 4. Skin effect in eddy current testing refers to: A. Surface contamination B. Current concentrated near surface C. Material melting D. Magnetic saturation Rationale: Eddy currents are strongest at the surface and decrease with depth. Correct Answer: B. Current concentrated near surface 5. Which material property most strongly affects eddy current response? A. Density B. Electrical conductivity
8. The unit of frequency in eddy current testing is: A. Tesla B. Hertz C. Ohm D. Volt Rationale: Frequency of alternating current is measured in Hertz (Hz). Correct Answer: B. Hertz 9. Which coil type provides the best sensitivity for small surface cracks? A. Encircling coil B. Bobbin coil C. Surface probe coil D. Ring coil Rationale: Surface probes are designed for localized high sensitivity inspections. Correct Answer: C. Surface probe coil 10. Lift-off effect refers to changes caused by: A. Material thickness B. Probe distance from surface
C. Temperature only D. Frequency change Rationale: Lift-off is the variation in signal due to spacing between probe and surface. Correct Answer: B. Probe distance from surface
11. Which of the following is a common application of eddy current testing? A. Detecting subsurface porosity in concrete B. Detecting cracks in aircraft structures C. Measuring liquid level in tanks D. Identifying biological tissues Rationale: ECT is widely used in aerospace for crack detection in conductive metals. Correct Answer: B. Detecting cracks in aircraft structures 12. Conductivity in eddy current testing is measured in: A. Siemens per meter B. Newtons C. Joules D. Pascals Rationale: Electrical conductivity is measured in Siemens per meter (S/m). Correct Answer: A. Siemens per meter
C. Power switch D. Calibration block Rationale: The probe coil generates the alternating magnetic field required for eddy currents. Correct Answer: B. Probe coil
16. A disadvantage of eddy current testing is: A. Requires liquid couplant B. Cannot detect surface defects C. Only works on conductive materials D. Requires radiation Rationale: ECT only works on conductive materials. Correct Answer: C. Only works on conductive materials 17. Which of the following is a unitless measurement in eddy current testing? A. Conductivity B. Phase angle C. Voltage D. Frequency Rationale: Phase angle is measured in degrees, making it dimensionless. Correct Answer: B. Phase angle
18. Eddy currents flow in which direction relative to the primary field? A. Parallel B. Random C. Opposing the change D. Vertical only Rationale: Eddy currents oppose the change in magnetic flux (Lenz’s Law). Correct Answer: C. Opposing the change 19. Lenz’s Law states that induced current: A. Enhances original field B. Opposes change in magnetic field C. Is independent of flux D. Eliminates resistance Rationale: The induced current always opposes the change causing it. Correct Answer: B. Opposes change in magnetic field 20. Which material property increases eddy current penetration depth? A. High conductivity B. High frequency
23. Signal amplitude in ECT is mainly affected by: A. Operator height B. Defect size and conductivity change C. Weather conditions D. Probe color Rationale: Larger defects or conductivity changes produce stronger signals. Correct Answer: B. Defect size and conductivity change 24. Which of the following best describes impedance in ECT? A. Resistance only B. Opposition to AC current flow C. Voltage increase D. Magnetic flux density Rationale: Impedance is the total opposition to alternating current in the coil. Correct Answer: B. Opposition to AC current flow 25. Which testing method is most similar to eddy current in principle? A. Radiographic testing B. Magnetic particle testing C. Ultrasonic testing D. Dye penetrant testing
Rationale: Magnetic particle testing also relies on electromagnetic principles. Correct Answer: B. Magnetic particle testing
26. What is the primary purpose of calibration in ECT? A. Increase probe size B. Ensure accuracy and repeatability C. Change material conductivity D. Reduce noise permanently Rationale: Calibration ensures instrument response is accurate and reliable. Correct Answer: B. Ensure accuracy and repeatability 27. Which factor reduces eddy current strength? A. High conductivity B. Low resistivity C. Increased lift-off D. Low frequency Rationale: Increased distance reduces induced current strength. Correct Answer: C. Increased lift-off
31. Which material has the best response in ECT? A. Wood B. Plastic C. Copper D. Glass Rationale: Conductive materials like copper give strong eddy current signals. Correct Answer: C. Copper 32. What is the role of phase shift? A. Measure color B. Identify defect depth/type C. Increase voltage D. Reduce noise Rationale: Phase shift helps distinguish flaw characteristics. Correct Answer: B. Identify defect depth/type 33. Which coil is used for inspecting tubes internally? A. Surface coil B. Encircling coil C. Bobbin coil D. Pancake coil
Rationale: Bobbin coils are designed for internal tube inspection. Correct Answer: C. Bobbin coil
34. What is the main cause of noise in ECT signals? A. Material color B. Surface roughness C. Operator speed D. Voltage stability only Rationale: Surface conditions create signal noise. Correct Answer: B. Surface roughness 35. Which law governs eddy current formation? A. Newton’s Law B. Ohm’s Law C. Lenz’s Law D. Hooke’s Law Rationale: Lenz’s Law explains direction of induced currents. Correct Answer: C. Lenz’s Law 36. What is the effect of increasing conductivity? A. Decreases eddy currents B. Increases penetration depth
39. Which of the following affects signal amplitude? A. Probe lift-off B. Material shape only C. Lighting conditions D. Gravity Rationale: Lift-off changes coupling strength. Correct Answer: A. Probe lift-off 40. Which test standard is commonly used in ECT? A. ASTM E B. ISO 9001 only C. AWS D1. D. ASME VIII only Rationale: ASTM E1004 relates to conductivity and ECT standards. Correct Answer: A. ASTM E 41. Which is NOT measured directly by ECT? A. Conductivity B. Crack detection C. Hardness directly D. Thickness indirectly Rationale: Hardness is not directly measured. Correct Answer: C. Hardness directly
42. What is the purpose of reference standards? A. Increase signal noise B. Calibration and comparison C. Reduce conductivity D. Change frequency Rationale: Standards ensure accuracy and repeatability. Correct Answer: B. Calibration and comparison 43. What happens when probe speed increases? A. Signal improves B. Resolution may decrease C. Frequency increases D. Conductivity increases Rationale: High speed reduces signal resolution. Correct Answer: B. Resolution may decrease 44. What type of current is used in ECT? A. Direct current B. Alternating current C. Pulsed DC only D. Static current
C. Deep internal void D. Conductivity variation Correct Answer: C. Deep internal void
48. Which display is commonly used in modern ECT systems? A. Analog dial only B. Oscilloscope/Impedance plane C. Thermometer D. Pressure gauge Correct Answer: B. Oscilloscope/Impedance plane 49. What is the function of filtering in ECT? A. Increase lift-off B. Remove noise C. Increase conductivity D. Change frequency Correct Answer: B. Remove noise 50. What is eddy current density highest at? A. Core of material B. Surface of conductor C. Air gap D. Insulator
Correct Answer: B. Surface of conductor
51. Which material gives weakest response in ECT? A. Copper B. Aluminum C. Steel D. Plastic Correct Answer: D. Plastic 52. What does conductivity variation indicate? A. Color change B. Material property change or defect C. Weight change D. Temperature only Correct Answer: B. Material property change or defect 53. Which factor improves sensitivity? A. Lower frequency B. Higher lift-off C. Higher frequency D. Larger probe distance Correct Answer: C. Higher frequency
