ET II General - Set 2
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1.
Eddy currents induced by a surface coil flow in:
2.
For an encircling coil around a solid non-magnetic bar, the eddy current density at the center of the bar is:
3.
What causes the skin effect, which concentrates eddy currents near the surface?
4.
An aluminum alloy skin (ρ = 5.0 µΩ·cm, μr = 1) is tested at 25 kHz. Applying δ(mm) = 50·√(ρ/(f·μr)), its standard depth is about:
5.
Using f = 2500·ρ/(μr·δ²), what frequency gives a standard depth of 0.5 mm in an alloy with ρ = 4.0 µΩ·cm and μr = 1?
6.
Which quantity is NOT a variable in the standard depth equation δ = 1/√(π·f·μ·σ)?
8.
Which of the following generally lowers the electrical conductivity of a metal?
9.
Relative permeability μr of a material is defined as:
10.
On a B-H magnetization curve, the permeability at a given point is:
11.
On a hysteresis loop, the magnetizing force needed to bring the flux density back to zero is called the:
12.
With inductance unchanged, a coil's inductive reactance doubles when:
13.
In a purely inductive AC circuit, voltage and current are:
14.
In the transformer model of eddy current testing, the test part behaves like:
15.
Starting from the air point, a surface probe touched in turn on titanium, stainless steel, aluminum and copper gives points that:
16.
Why is the 'knee' of the conductivity curve a preferred operating region on the impedance plane?
17.
On the impedance plane, the direction in which a signal moves is its ___, and the length of the movement is its ___.
18.
For a surface probe on plate, the plate thickness stops affecting the reading once the thickness exceeds about:
19.
Phase discrimination in eddy current testing works because:
20.
A rotating bolt-hole probe turns at 1200 rpm in a 10 mm diameter hole. For a crack 1 mm long, the flaw signal frequency is about:
21.
As a rule of thumb, how should the test frequency compare with the flaw signal frequency produced by scanning?
22.
Setting the high-pass filter too high on an absolute channel will most likely:
23.
Which noise source is best reduced by single-point grounding and undamaged shielded cables?
24.
If the instrument gain is reduced by 6 dB, the signal amplitude becomes about:
25.
In an eddy current instrument, the phase-sensitive detector:
26.
A calibrated meter readout differs from an uncalibrated one because it:
27.
The main advantage of an eddy current array (ECA) probe is:
28.
A Hall element's output voltage is proportional to:
29.
An external-reference differential arrangement compares:
30.
Why does a surface probe give a large signal as it approaches the edge of a plate, even with no flaw present?
31.
In a two-frequency support-plate suppression mix, the lower auxiliary frequency is chosen mainly because it:
32.
In remote field testing, the phase lag and amplitude of the detected signal are mainly related to:
33.
In RFT, the region next to the exciter, where the field is confined inside the tube and decays rapidly, is the:
34.
An ACFM butterfly plot is formed by plotting:
35.
In ACFM, the depth of the Bx dip over a crack is mainly related to:
36.
Under SNT-TC-1A 2024, the minimum number of questions on an ECT Specific examination for Level I or Level II is:
37.
Under SNT-TC-1A 2024, color contrast differentiation should be demonstrated:
38.
A candidate fails an ECT certification examination. Before re-examination, SNT-TC-1A recommends:
39.
Under SNT-TC-1A, the maximum recommended interval for recertification of ECT Level I and Level II personnel is:
40.
Under SNT-TC-1A, who grants certification to an ECT Level II technician?