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EC L1 > Review Questions > Flashcards

Review Questions Flashcards

1
Q

A test specimen used as the basis for calibrating test equipment or as a comparison when evaluating test results is called a what?

A

Reference standard

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2
Q

The ratio of response/amplitude from signals of interest to response/amplitude of indications that contain no useful info for the test conducted are called what?

A

Signal to noise ratio

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3
Q

When conducting an EC test, using a differential coil arrangement that compares an external reference standard with the test specimen, the system should be nulled or balanced with what?

A

A reference standard in one coil and an acceptable specimen in the other

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4
Q

The impedance of an EC test coil will increase if what?

A

The test frequency increases

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5
Q

What would normally be considered the best fill factor when testing straight tubing with an encircling/feed through coil?

A

.95 (95%)

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6
Q

When a magnetic metal part is placed in an EC test coil, the impedance of the coil will be changed by which property in the part?

A

Conductivity, permeability and dimensions

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7
Q

An eddy current is a circulating electrical current induced in a conducting article by what?

A

An alternating magnetic field

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8
Q

When testing tubing with an inside diameter coil, most of the eddy currents will be where ?

A

Flowing around the inside diameter of tubing

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9
Q

An eddy currents test coil’s opposition to flow of alternating current is called what?

A

Impedance

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10
Q

An increase in impedance of EC test coil will do what to current flow in coil?

A

Decrease in current flow through test coil

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11
Q

What 3 things will affect the impedance of an encircling EC test probe?

A
  1. Conductivity
  2. Permeability
  3. Fill factor
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12
Q

Eddy current test coils that are wound to form a wide coil would normally be used to detect what?

A

Changes in conductivity

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13
Q

Eddy current test coils that are wound to form a narrow coil would normally be used to detect what?

A

Small surface defects

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14
Q

DC saturation coils are usually used when testing what type of material?

A

Steel

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15
Q

A single absolute coil arrangement can be used in what (3)?

A
  1. Probe
  2. Encircling
  3. ID coils
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16
Q

The primary purpose of the secondary winding in an eddy current coil is to what?

A

Detect changes in eddy current flow

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17
Q

When attempting to determine the exact point of a discontinuity, the test system should include what?

A

A probe coil

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18
Q

It’s possible to sort various non-magnetic alloys of metal by means of eddy current testing when there’s what?

A

A unique range of conductivity values for each alloy

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19
Q

What’s an example of a product that would be most applicable to a test using an ID coil?

A

Bolt hole

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20
Q

What would be a method to reduce irrelevant indications when EC testing ferromagnetic materials?

A

Use a DC saturation coil to magnetically saturate the test specimen

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21
Q

Eddy currents are circulating currents induced in a conducting material by what?

A

Varying magnetic fields

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22
Q

In order to generate measurable eddy currents in a test specimen, what must the specimen be?

A

A conductor

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23
Q

All ferromagnetic materials that have been magnetically saturated to suppress permeability variations, may retain a certain amount of magnetization which is referred to as what?

A

Residual magnetism

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24
Q

An AC current flowing in a conductor will set up a magnetic field where?

A

Around the conductor

25
Q

When conducting an eddy current test on tubing, the magnitude of the indication caused by a discontinuity is dependant on what 3 things?

A

Depth, width and length of discontinuity

26
Q

A coil’s magnetic field may be viewed as a distribution of lines of flux around the coil. The number of lines in a unit area is called what?

A

Flux density

27
Q

How do eddy currents travel?

A

In closed paths

28
Q

What is the condition of balance in a device or system which results in zero output?

A

Null balance

29
Q

What is a unit of flux density?

A

Gauss

30
Q

What is the region around the magnet called that will attract other pieces or iron or steel to it?

A

Magnetic field

31
Q

Which eddy current arrangement does not make a comparison between 2 sections of a specimen?

A

Absolute coil

32
Q

A length of tubing with a notch running end to end, having uniform width & depth, when tested with an encircling self referencing differential coil will produce what type of indication?

A

No indication

33
Q

Spinning, probe type eddy current instruments are most useful in detection of what?

A

The smallest surface blemishes

34
Q

One principle advantage of a spinning probe eddy current instrument is what?

A

The ability to find the circumferential position of defects

35
Q

At any given instant during a test, a spinning probe will be inspecting what area?

A

The area defined by the size of coil

36
Q

What causes a phase shift in an eddy current coil?

A

Change in ratio of inductive reactance to resistance

37
Q

When eddy current testing a non ferrous specimen, a discontinuity will do what to conductivity of specimen?

A

Decrease the effective conductivity of specimen

38
Q

Most basic eddy current systems monitor changes in voltage due to changes in what?

A

Impedance

39
Q

An increase in impedance of an eddy current test coil will cause a what in test coil?

A

Decrease in current flow through test coil

40
Q

The ideal fill-factor percentage of an ID bobbin probe in tube inspections would be what?

A

80% to 95%

41
Q

When material temperature increases, what happens to the eddy currents?

A

They get weaker

42
Q

Probe wobble is a form of what?

A

Lift off

43
Q

According to Ohm’s Law, in any electrical circuit, the voltage divided by the circuit impedance is equal to what?

A

Current flow

44
Q

Who’s law states that when an alternating voltage induces an EMF, the induced EMF in opposition to the change causing it?

A

Lenz’s Law

45
Q

What is a device that stores electrical energy within a specified volume?

A

Capacitor

46
Q

In a fixed magnetic field, how would the compass needle arrange itself in relation to the lines of force?

A

Parallel

47
Q

How can direct current be used to induce eddy currents?

A

If the test piece or conductor is moved cylindrically or

48
Q

1 mA is how many amps?

A

0.001 A

49
Q

A secondary field is generated by the test object and how is it comparable to the primary field?

A

Opposite the primary field but much smaller

50
Q

When a non ferromagnetic part is placed in the test coil, what happens to the coil’s voltage?

A

Decreases

51
Q

Eddy currents generated in a test object flow where?

A

The same plane as the coil is wound

52
Q

A spinning probe would most likely be what type of coil?

A

Probe coil

53
Q

How is an absolute coil measurement made?

A

Without reference to or a direct comparison with a standard

54
Q

When coils in a differential arrangement are affected simultaneously with the same test object variables, what will the output signal read?

A

0 or near 0

55
Q

A hybrid coil is composed of two or more coils. What are the coils like?

A

Maybe of widely different dimensions

56
Q

Inductance is comparable to what?

A

Inertia

57
Q

What is the unit for inductance?

A

Henry

58
Q

What type of crack detector may use the uncalibrated meter approach?

A

Single frequency crack detector

EC L1 (3 decks)

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