Eddy Current Testing (ET) Level I Practice Test

As test material conductivity increases, what happens to the coil's inductive reactance?

test coil inductive reactance increases back voltage increases test coil inductive reactance remains constant test coil inductive reactance decreases

Correct Answer:

test coil inductive reactance decreases

Explanation:

In eddy current testing, the material’s conductivity determines how strongly eddy currents are formed when the coil’s field changes. These eddy currents produce a magnetic field that opposes the coil’s field, reducing the net magnetic flux linked by the coil. With higher conductivity, the opposing field is stronger, so the effective inductance seen by the coil drops. Since inductive reactance at a given frequency is X_L = ωL, a lower inductance means a smaller inductive reactance. So, as conductivity increases, the coil’s inductive reactance decreases. The idea that back voltage would increase isn’t consistent with the reduced inductance in this scenario.

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