Level 1 Question [Ref]
1 Which of the following conditions is not necessary for eddy current testing? [ECM ] a) electrical contact b) specimen conductivity c) an alternating magnetic field d) induced electrical current
2 Which of the following is not a mandatory component in a "basic" eddy current test apparatus? [ECM ] a) an AC source b) a coil (probe) c) an impedance plane d) a volt meter
3 Which of the following is not a probe configuration used in eddy current testing? [ECM ] a) self inductance (single coil) b) send-receive (2 coils) c) magnetic reaction (coil & Hall detector) d) semi-conductor reaction (2 Hall detectors)
4 The sense or direction of a magnetic field around a conductor is most commonly determined using [ECM ] a) Lenz's Law b) Ohm's Law c) a Rowland Ring d) the right hand rule
5 Tesla or Webers per square metre (Wb/mý) are units of [ECM ] a) eddy current b) impedance c) reluctance d) magnetic flux density
6 If the electric current in a coil is doubled the magnetic flux density [ECM ] a) halves b) remains unchanged c) doubles d) quadruples
7 An increase in which of the following would result in the increase of magnetic flux density (B) in a solenoid? [Burns ] a) core permeability b) number of coil turns c) current in the coil d) all of the above
8 A voltage in induced in a region of space when there exists a changing magnetic field. This is a statement of [ECM ] a) Faraday's Law b) Oersted's Law c) Helmholtz's Theorem d) Ohm's Law
9 Lenz's Law states [Burns ] a) an alternating magnetic field induces an alternating voltage b) the magnitude of induced current is a function of magnetic flux through a circuit c) the induced EMF is opposite to the change causing it d) í = B A cosà where B= flux density, A = circuit area and à = the angle between B and the circuit area A
10 The back EMF opposing the inducing EMF is a result of [ECM ] a) the Hall effect b) eddy current flow c) geo-magnetic reversals d) weak nuclear forces
11 Which of the following is not an example of electromechanical energy conversion devices? [Ramshaw ] a) a dry cell battery b) a generator or alternator c) a microphone d) an electric motor
12 An eddy current test system closely approximates a transformer. In this approximation, what would the "secondary coil" be represented by? [ECM ] a) the induced eddy currents b) the eddy current probe c) the test sample d) a Hall detector used as a receiver
13 By convention, the direction of a magnetic line of force is represented by an arrow on a line. The arrow would point in the direction [Jacobowitz ] a) in which a unit north pole would be moved b) in which a unit south pole would be moved c) perpendicular to the plane of the line d) indicated by the thumb in the left hand rule
14 The magnetic line of force is [Jacobowitz ] a) a mythical quantity b) a imaginary but useful concept c) equal to 1gm mass when converted by Einstein's equation d) 1 micron diameter and 10 microns long
15 The principal cause of magnetism in a naturally magnetic substance is [Jacobowitz ] a) hysteresis b) the weak nuclear force c) uncompensated electron spin d) graviton concentration in the Domain wall
16 The number of lines of magnetic flux divided by a unit area is the [Jacobowitz ] a) permeability b) flux density c) pole strength d) field intensity
17 Moving a direct current carrying conductor up and down near a conductive test piece will result in [Handbook ] a) no current flow in the test piece b) DC being induced in the test piece c) AC being induced in the test piece d) a short circuit
18 The relationship between electric current flow, electromotive force and resistance to electric current flow is described by [Jacobowitz ] a) Lenz's law b) Ohm's law c) Faraday's rule d) the ampere-ohm equation
19 Another term for voltage is [Jacobowitz ] a) electromotive force b) magnetomotive force c) potential drop d) both a and c
20 In order to use a galvanometer (which normally measures currents in the range of milliamps) as an ammeter measuring 10 to 20 amps you would put a _________ in ___________ with the galvanometer. [Burns ] a) resistor, series b) resistor, parallel c) capacitor, series d) capacitor, parallel
21 Conductance is an electrical quantity which can also be defined as the reciprocal of [Jacobowitz ] a) inductance b) resistance c) resistivity d) reluctance
22 When an eddy current probe is brought near a conductive sample the net magnetic flux in the system [ECM ] a) increases b) decreases c) remains unchanged d) drops to zero when the part is contacted
23 Eddy current density in a sample is [ECM ] a) proportional to the conductivity of the sample b) proportional to the permeability of the sample c) inversely proportional to the depth from the surface of the sample d) all of the above
24 Strictly speaking, the standard skin depth equation; J/Jo = (e^-á) sin (wt-á), is true for only [ECM ] a) thick material and planar magnetic fields b) tubular products c) thin plate inspection d) all of the above
25 At 2 standard depths of penetration, eddy current density is about ____ that at the surface. [ECM ] a) 0,66 b) 0,37 c) 0,14 d) 0,09
26 When inspecting a rod with an encircling coil the eddy current density at the centre of the rod is zero for [ECM ] a) rods with diameters greater than 2ë b) rods with radius greater than 2ë c) all conditions d) no condition, a slight current density will always exist
27 Phase lag of eddy currents in a sample is dependent on [ECM ] a) depth into the sample b) resistivity of the test piece c) relative magnetic permeability of the sample d) all of the above
28 Why are eddy current coils not made using iron wire? [Blitz ] a) to avoid hysteresis effects b) to make mathematical calculations easier c) to prevent excessive heat build-up d) for cathodic breakdown considerations
29 The higher the value of inductance for a given frequency the greater the degree of [Blitz ] a) balance ability b) sensitivity c) Q factor d) capacitive reactance
30 The transmit-receive or transformer style probe provides [Blitz ] a) improved s/n ratio b) increased sensitivity to deeper defects c) both a and b d) no advantage over single coil probes