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31 questions from the nondestructive testing (level ii) practice test.
10 questions, graded as you go, with the reason for every answer. No sign-up.
Passing current end to end through a solid bar clamped between the heads of a wet horizontal unit (a head shot) produces which kind of field?
D. Circular
Current flowing along a conductor sets up a magnetic field in circles around the current path, so a head shot magnetises the bar circularly. A longitudinal field needs a coil or a yoke.
Reference: ASTM E709, circular magnetisation; right-hand rule
Placing a shaft inside a current-carrying coil produces which kind of field in the shaft?
B. Longitudinal
The field inside a coil runs along the coil's axis, so a part lying in the coil is magnetised lengthwise with a pole at each end. Circular fields come from passing current through the part or through a central conductor.
Reference: ASTM E709, longitudinal magnetisation
A head shot on a solid shaft is the correct technique for finding discontinuities that run in which direction?
D. Lengthwise, along the shaft axis
The head shot's field circles the shaft, so it is crossed by discontinuities running lengthwise, such as seams. A useful check: the discontinuities found are those roughly parallel to the direction of current flow. Transverse discontinuities need a coil shot.
Reference: ASTM E709, circular magnetisation