Eddy Current Level I Flashcards
1) In electromagnetic testing, which of the following is not a source of noise?
a. Geometrical changes
b. Permeability variations within the test object
c. Electrical interference
d. Coil size
d. Coil size
2) The ratio of the response or amplitude from signals of interest to the response or amplitude of indications that contain no useful information for the test being conducted is referred to as:
a. aspect ratio
b. signal-to-noise ratio
c. the conductivity-to-permeability ratio
d. the reactance-to-resistance ratio
b. signal-to-noise ratio
3) Which of the following is not a basic component of an eddy current test system?
a. Amplifier
b. Sine wave generator
c. Wear-resistant tape
d. Filter
c. Wear-resistant tape
4) When conducting an eddy current test using a differential comparison coil arrangement that compares an external reference standard with the test specimen, the system should be nulled or balanced:
a. with only the reference standard in one coil
b. with the reference standard in one coil and an acceptable test specimen in the other coil
c. with the reference standard in one coil and an unacceptable test specimen in the other coil
d. with only the test specimen in one coil
b. with the reference standard in one coil and an acceptable test specimen in the other coil
5) The impedance of a test coil will increase if the:
a. test frequency increases
b. inductive reactance of the coil decreases
c. inductance of the coil decreases
d. resistance of the coil decreases
a. test frequency increases
6) Some of the products commonly tested using encircling coils are:
a. rods, tubes, and wire
b. plate when volumetrically inspected
c. sheets and metalized foil
d. structural steel welds
a. rods, tubes, and wire
7) Which of the following would normally be considered the best fill factor when testing straight tubing with an encircling or feedthrough coil?
a. 1.75 (175%)
b. 0.95 (95%)
c. 0.50 (50%)
d. 0.25 (25%)
b. 0.95 (95%)
8) When a metal part is placed in an eddy current test coil, the impedance of the coil will be changed by all of the following properties of the part except:
a. conductivity
b. dimensions
c. permeability
d. nonconductive coating
d. nonconductive coating
9) An eddy current test makes use of electrical current induced in a conductive article by:
a. gamma rays
b. an alternating magnetic field
c. a piezoelectric force
d. a decay process
b. an alternating magnetic field
10) The conductivity of a material can be altered by changing the:
a. amount of paint on the part surface
b. chemistry of the part
c. length of the part
d. volume of the part
b. chemistry of the part
11) The depth to which eddy currents are induced in the material is determined mostly by the:
a. thickness of the material
b. diameter of the material
c. geometrical shape of the material
d. test frequency
d. test frequency
12) When testing plate with a probe coil, it is noted that the eddy current output indication varies as the distance from the coil to the surface of the test part varies. The term used to describe this action is:
a. fill factor
b. liftoff
c. phase differentiation
d. edge effect
b. liftoff
13) The main purpose for spring-loaded eddy current probe coils is to:
a. minimize liftoff variations
b. minimize wear on the probe
c. reduce operator fatigue
d. eliminate edge effect
a. minimize liftoff variations
14) Liftoff is utilized in:
a. measuring permeability changes
b. measuring conductivity changes
c. measuring the thickness of nonconductive coatings
d. determining proper test frequency
c. measuring the thickness of nonconductive coatings
15) In eddy current test systems where encircling coils are used, coupling efficiency is referred to as:
a. liftoff
b. edge effect
c. fill factor
d. phase differentiation
c. fill factor
16) When inspecting products with a uniform cross section, an eddy current signal is produced when the leading end or trailing end of the product approaches the test coil. This phenomenon is referred to as:
a. liftoff
b. end effect
c. fill factor
d. phase discrimination
b. end effect
17) Which of the following conditions would be the most difficult to detect when eddy current testing a rod with an encircling coil?
a. A deep surface crack that has a depth of 30% of the rod diameter
b. A small inclusion in the center of the rod
c. A 5% change in diameter
d. A 10% change in conductivity
b. A small inclusion in the center of the rod
18) When testing tubing with a bobbin coil, most of the eddy currents:
a. flow in a longitudinal direction down the tubing
b. flow radially in the tube
c. flow around only the outside diameter of the tubing
d. flow around the inside diameter of the tubing
d. flow around the inside diameter of the tubing
19) Which of the following test frequencies would produce eddy currents with the largest depth of penetration?
a. 100 Hz
b. 10 kHz
c. 1 MHz
d. 10 MHz
a. 100 Hz
20) A test coil’s opposition to the flow of alternating current, causing the current to lag behind the voltage, is called:
a. resistance
b. inductive reactance
c. impedance
d. capacitive reactance
b. inductive reactance
21) An increase in the impedance of a test coil will:
a. produce an increase in the voltage through the test coil
b. cause a decrease in the measured voltage across the test coil
c. not affect the voltage in the test coil
d. decrease the voltage applied to the coil
a. produce an increase in the voltage through the test coil
22) Which of the following will not affect the inductance of a test probe?
a. Test frequency
b. Number of turns of wire in the coil
c. Coil width
d. Coil cross-sectional area
a. Test frequency
23) When a test coil consists of a double winding arrangement and one winding is referred to as a primary winding, the other winding is referred to as the:
a. absolute winding
b. secondary winding
c. phase winding
d. differential winding
b. secondary winding
24) Large-diameter surface scanning coils would most likely be used for the detection of:
a. pitting
b. small inclusions
c. changes in conductivity
d. porosity
c. changes in conductivity
25) Small-diameter probe coils would typically be used for the detection of:
a. slow changes in dimensions
b. gradual changes in conductivity
c. variation in heat treatment
d. small surface discontinuity
d. small surface discontinuity
26) Direct current saturation coils would most likely be used when testing:
a. carbon steel
b. aluminum
c. copper
d. brass
a. carbon steel
27) An absolute coil arrangement can be used in:
a. encircling coils only
b. probe coils only
c. probe and encircling coils only
d. probe, encircling, and inside diameter coils
d. probe, encircling, and inside diameter coils
28) Which of the following expresses the primary purposes of the secondary windings in an eddy current probe?
a. Induce eddy currents in the test specimen
b. Detect changes in the eddy current flow
c. Induce eddy currents in the test specimen and detect changes in the eddy current flow
d. Provide DC saturation
b. Detect changes in the eddy current flow
Which of the following eddy current test coil arrangements uses one area of the test specimen as a reference standard against which another area on the same specimen is simultaneously compared?
a. Single absolute coil
b. Double absolute coil
c. DC saturation coil
d. Differential coil
d. Differential coil
30) Reference standards used for electromagnetic testing:
a. must contain artificial discontinuities such as notches and drilled holes
b. must contain natural discontinuities such as cracks and inclusions
c. must be free of measurable discontinuities
d. may contain artificial or natural discontinuities or be free of discontinuities depending on the test system and the type of test being conducted
d. may contain artificial or natural discontinuities or be free of discontinuities depending on the test system and the type of test being conducted
31) A tool used to ensure that the test system does not drift during a test cycle is called a:
a. DGS standard
b. calibration standard
c. mix algorithm
d. probe
b. calibration standard
32) Which of the following could not be tested by the electromagnetic testing method?
a. A 102 mm (4 in.) thick plate to be tested for small discontinuities throughout the plate
b. Tubing to be tested for surface cracks
c. Rod to be tested for laps and seams
d. Tubing to be tested for variations in outside diameter
a. A 102 mm (4 in.) thick plate to be tested for small discontinuities throughout the plate
33) Which of the following is not true about an eddy current test?
a. It can be used for high-speed testing
b. It can accurately measure conductivity
c. It can be set up to provide high sensitivity to small discontinuities
d. It can penetrate up to 152 mm (6 in.) in a test part
d. It can penetrate up to 152 mm (6 in.) in a test part
34) The entire circumference of a tube can be evaluated at one time when using:
a. an encircling coil
b. a bobbin coil
c. a pencil probe
d. a pancake coil
a. an encircling coil
35) When attempting to determine the exact circumferential location of a discontinuity in a tube, the test system should include:
a. a phase shifter
b. a probe coil
c. an attenuator
d. a penetrameter
b. a probe coil
36) It is often possible to sort various nonferromagnetic alloys of a metal by means of an eddy current test when:
a. there is a unique range of permeability values for each alloy
b. there is a unique range of conductivity values for each alloy
c. the direction of induced eddy currents varies for each alloy
d. the magnetic domains for each alloy are different
b. there is a unique range of conductivity values for each alloy
37) Which of the following products would be most applicable to a test using an inside coil?
a. Sheet
b. Rod
c. Bolt hole
d. Coating thickness
c. Bolt hole