Questions & Answers
- Electromagnetic Testing (ET) Level - 1 - 2 - 3

Level 3	Question	[Ref]
1	Electromechanical energy conversion is possible due to	[Ramshaw]
	a) electric fields
	b) magnetic fields
	c) both a and b
	d) none of the above, energy conversion by electromechanics is not possible
2	The intensity of a magnetic field that a unit magnetic pole experiences a force of one dyne is one	[Jacobowitz]
	a) oersted
	b) Tesla
	c) ohm-cm
	d) gauss
3	A single magnetic line of flux is given the unit	[Jacobowitz]
	a) dyne
	b) oersted
	c) maxwell
	d) tesla
4	Alignment of the magnetic domains in iron by an external field result in	[Jacobowitz]
	a) hysteresis
	b) eddy currents
	c) magnetization
	d) permeability
5	The force between point magnetic poles is	[Jacobowitz]
	a) proportional to pole strength
	b) inversely proportional to the square of the distance separating them
	c) both a and b
	d) the opposite of a and b
6	The product of current in amperes times time in seconds gives units of	[Jacobowitz]
	a) abvolts
	b) Coulombs
	c) electro-stats
	d) Hertz
7	If 20 coulombs of charge passes a point in 5 seconds, the electric current value would be	[Jacobowitz]
	a) 4 amperes
	b) 100 amperes
	c) 0.8 amperes
	d) 20 amperes
8	Eddy currents are an undesirable feature in	[Handbook]
	a) AC power transformers
	b) carbon composite materials
	c) eddy current testing
	d) ultrasonic testing
9	Which of the following will have an effect on the electrical resistance of a wire?	[Jacobowitz]
	a) inherent resistivity
	b) length and cross-sectional area
	c) temperature
	d) all of the above
10	Resistance of a piece of wire is a function of	[Jacobowitz]
	a) wire length
	b) cross sectional area of the wire
	c) resistivity of the material the wire is made of
	d) all of the above
11	The temperature coefficient of resistance of a pure metallic conductor is always	[Jacobowitz]
	a) negative
	b) positive
	c) zero
	d) unity
12	A negative thermal coefficient of resistivity would be characteristic of	[Jacobowitz]
	a) all pure metals
	b) some semi conductors
	c) insulators
	d) materials conductivity > 100% IACS
13	The decrease in eddy current density with increasing depth from the surface is	[ECM]
	a) linear
	b) exponential
	c) logarithmic
	d) sinusoidal
14	The time dependent component of the skin depth equation indicates	[ECM]
	a) flux density decreases with depth
	b) current density decreases with depth
	c) phase lag of the signal with depth
	d) all of the above
15	For the calculation for eddy current density to apply, a sample should be relatively thick. The minimum thickness to allow the simple equation to apply is about __________ ë (where ë is the standard depth of penetration).	[ECM]
	a) 0.5
	b) 2
	c) 5
	d) 25
16	To ensure planar shaped magnetic field _________ probes are needed.	[ECM]
	a) large diameter
	b) long
	c) zig-zag
	d) either a or b depending on whether plate or tube testing is being done
17	Phase lag in the test sample for a void at 1 standard depth of penetration is	[ECM]
	a) 1 radian
	b) 90ø
	c) both a and b
	d) none of the above, it cannot be determined from the given information
18	For the purpose of determining electrical characteristics of a coil/sample combination, capacitance can be an important factor in	[ECM]
	a) the sample
	b) the probe cables
	c) the probe coil
	d) all of the above
19	The inductive reactance component of an eddy current probe coil's impedance will ___________ with increasing AC frequency.	[ECM]
	a) increase
	b) decrease
	c) remain unchanged
	d) react unpredictably
20	In the eddy current probe circuit the capacitive component of its impedance is __________degrees out of phase with its inductive component.	[ECM]
	a) 0
	b) 90
	c) 180
	d) 270
21	The "phase" of the impedance in an AC circuit is found from	[ECM]
	a) Arcsin (R/x)
	b) Arccos (R/x)
	c) Arctan (R/x)
	d) Arctan (x/R)
22	In eddy current terminology phasors are used for	[ECM]
	a) voltage amplitude and phase representation
	b) repairing broken solder joints
	c) fusing near surface defects
	d) terminating technicians who make incorrect evaluations
23	On the ideal impedance diagram the effect of reducing mutual coupling between probe and sample would be to have the impedance point	[ECM]
	a) move up the curve
	b) move down the curve
	c) trace smaller semi-circles
	d) trace larger semi-circles
24	The impedance method of eddy current testing uses	[ECM]
	a) two coils
	b) changes in voltage across the primary coil
	c) changes in voltage across the secondary coil
	d) spring loaded probes only
25	Variations in the flow of eddy currents caused by flaws in the test piece are monitored as voltage fluctuations in the secondary coil in the	[ECM]
	a) send-receive method of ECT
	b) impedance method of ECT
	c) resonance method of ECT
	d) potential drop method
26	When a probe/sample combination is modelled as an "equivalent circuit," the secondary circuit load equivalent would be considered a(n)	[ECM]
	a) resistive load in parallel with the coil's inductive reactance
	b) inductive load in parallel with the coil's inductive reactance
	c) capacitive load in series with the coil's inductive reactance
	d) short circuit
27	An increase in probe diameter will move the operating point on the impedance curve	[ECM]
	a) up
	b) down
	c) to a point inside the original curve
	d) to a point outside the original curve
28	An inductive and a resistive impedance change in the test coil resulting when an operating eddy current probe is moved near a conductive test sample is represented on a(n)	[ECM]
	a) standard penetration chart
	b) phase correction graph
	c) 'E' meter
	d) impedance graph display
29	Multifrequency techniques using differential coils are	[Blitz]
	a) best for detecting large volume defects
	b) best for detecting small cracks and pits
	c) used to size dents
	d) never successful
30	When access for inspection of a pipe is from the inside in the remote field eddy current technique, the receiver coil is	[Blitz]
	a) an internal axial probe
	b) an array of surface coil probes
	c) both a and b
	d) the same coil as used for excitation

References (NDT TestMaker software)

1. [Handbook] ASNT; Nondestructive Testing Handbook, vol. four, Electromagnetic Testing, Second Edition, ASNT, 1986
2. [Jacobowitz] Jacobowitz,H.; Electricity Made Simple, Doubleday & Company, 1959
3. [Mix] Mix, P.E.,; Introduction to Non-Destuctive Testing, John Wiley & Sons, 1987
4. [ECM] V.S.Cecco, G.van Drunen and F.L.Sharp, Eddy Current Manual vol. 1, Chalk River Nuclear Laboratories, 1983
5. [Burns] D.M.Burns & S.G.G.MacDonald Physics for Biology and Premedical Students, Addison-Wesley Publishing Company, 1970
6. [Ramshaw] R.S.Ramshaw & R.G.van Heeswajk, Electromagnetic Fields and Forces University of Waterloo, Standford Educational Press, 1979
7. [Blitz] J.Blitz, Electrical and Magnetic Methods of Nondestructive Testing, Adam Hilger, IOP Publishing Ltd., 1991
8. [Techniques] D.E.Bray and D.McBride, Nondestructive Testing Techniques John Wiley & Sons, 1992
9. [Gardner] W.E.Gardner, Editor, Improving the Effectiveness and Reliability of Nondestructive Testing Pergamon Press, 1992
10. [ASME] American Society of Mechanical Engineers, ASME Section V, The American Society of Mechanical Engineers, 1992