Eddy Current Testing Level I (20 Questions)

Q.1    Generation of eddy currents depends on the principle of:

A.  wave guide theory.

B.  electromagnetic induction.

C.  magneto-restrictive forces.

D.  all of the above.

Q.2    A secondary field is generated by the test object and is:

A.  equal and opposite to the primary field.

B.  opposite to the primary field, but much smaller.

C.  in the same plane as the coil is wound.

D.  in phase with the primary field.

Q.3    When a non-ferromagnetic part is placed in the test coil, the coil's voltage:

A.  increases.

B.  remains constant because this is essential.

C.  decreases.

D.  shifts 90 degrees in phase.

Q.4    Eddy currents generated in a test object flow:

A.  in the same plane as magnetic flux.      
B.  in the same plane as the coil is wound.

C.  90 degrees to the coil winding plane.

D.  Eddy currents have no predictable direction.

Q.5    The discovery of electromagnetic induction is credited to:

A.  Arago.

B.  Oersted.

C.  Maxwell.

D.  Faraday.

Q.6    A standard depth of penetration is defined as the point in a test object where the relative eddy current density is reduced to:

A. 25 percent.

B. 37 percent.

C. 50 percent.

D. 100 percent.

Q.7    Calculate the standard depth of penetration at 10 kHz in copper; σ = 5.7 • 10⁷ mhos per meter.

A. 0.1 mm

B. 0.02 mm

C. 0.66 mm

D. 66 mm

Q.8    Differential coils are usually used in:

A.  bobbin coils.

B.  probe coils.

C. OD coils.

D. any of the above.

Q.9    When using a probe coil to scan a test object,______

A.  the object must be dry and polished.

B.  the object must be scanned carefully to insure inspection coverage.

C.  the object must be scanned in circular motions at constant speeds.

D.  the probe must be moving at all times to get a reading.

Q.10    A "spinning probe" would most likely be a (an):

A. bobbin coil.

B. ID coil.

C. OD coil.

D. probe coil.

Q.11    A "feed-through" coil is:

A. a coil with primary/secondary windings connected so that the signal is fed through the primary to the secondary.

B. an encircling coil.

C. an OD coil.

D. both B and C.

Q.12  When inspecting a tubular product with an encircling coil, which statement is not true?

A. OD discontinuities can be found.

B.  Axial discontinuity locations can be noted.

C. Circumferential discontinuity locations can be noted.

D. ID discontinuities can be found.

Q.13  An absolute coil measurement is made  

A. by comparing one spot on the test object to another.

B. without reference to or direct comparison with a standard.

C. only with probe coils.

D. by comparative measurement to a known standard.

Q.14  When coils in a differential arrangement are affected simultaneously with the same test object variables, the output signal

A. is directly proportional to the number of variables.

B. is "0" or near-"0."

C. is indirectly proportional to the number of variables.

D. is primarily a function of the exciting current.

Q.15Which coil type inherently has better thermal stability?

A. Bobbin

B. Absolute

C. OD                                                                                                                          

D. Differential

Q.16  A hybrid coil is composed of two or more coils. The coils -

A. must be aligned coplanar to the driver axis.

B. may be of widely different dimensions.

C. must be impedance-matched as closely as possible.

D. are very temperature sensitive.

Q.17  Proper selection of test coil arrangement is determined by:

A. shape of test object.

B. resolution required.

C. sensitivity required.

D. all of the above.

Q.18  A coil's resistance is determined by:

A. wire material.

B. wire length.

C. wire cross-sectional area.

D. all of the above.

Q.19  Inductance is analogous to:

A. force.

B. volume.

C. inertia.

D. velocity.

Q.20  The unit of inductance is the:

A. henry.

B. maxwell.

C. ohm.

D. farad.

ANSWER

1.B	2.B	3.C	4.B	5.D	6.B	7.C	8.D	9.B	10.D
11.D	12.C	13.B	14.B	15.D	16.B	17.D	18.D	19.C	20.A