GENERAL LEVEL 2 Flashcards
- Which of the following is not a property of magnetic lines of force?
(a) They form closed loops which do not cross
(b) The density increases with distance from the poles of a permanent magnet
(c) Hey are considered to have direction
(d) They seek paths of least magnetic resistance or least reluctance
(b) The density increases with distance from the poles of a permanent magnet
- Surrounding an electromagnet, the magnetic field is strongest:
(a) Immediately after the current ceases to flow
(b) While the magnetizing current ceases to flow
(c) At the time the magnetic particles are applied to the part
(d) Just prior to current reversal
(d) Just prior to current reversal
- The value of permeability is:
(a) A fixed value depending upon the type of material
(b) Between 1 and 100 for all ferromagnetic materials
(c) Between 0 and 10 for all ferromagnetic materials
(d) Dependent upon the amount of magnetizing force necessary to overcome
saturation
(a) A fixed value depending upon the type of material
- The flux density of the magnetism induced by a coil is affected by:
(a) The coil size
(b) The current in the coil
(c) The number of turns in the coil
(d) All of the above
(a) The coil size
(b) The current in the coil
(c) The number of turns in the coil
(d) All of the above
- How many turns of a coil will be needed to establish a longitudinal field in a steel
shaft that is 22.86 cm (9 inches) long and 7.62 cm (3 inches) in diameter? 3000
amperes magnetizing current is available, it is desired to magnetize the part in
accordance with the formula NI = 45,000/(L/D):
(a) 1
(b) 3
(c) 5
(d) 7
(c) 5
- How many ampere-turns are required to magnetize a part that is 40.6 cm (16 inches)
long and 5 cm (2 inches) in diameter?
(a) 9000 ampere-turns
(b) 5625 ampere-turns
(c) 2812 ampere-turns
(d) None of the above
(b) 5625 ampere-turns
- The lines of flux or force in a circularly magnetized ferromagnetic bar:
(a) Are aligned through the piece from the south to the north pole
(b) Are aligned through the piece from the north to the south pole
(c) Leave the south pole and enter the north pole
(d) Are contained within and around the part
(d) Are contained within and around the part
- In which magnetizing method is the current passed directly through the part, thereby
setting up a magnetic field at right angles to the current flow?
(a) Longitudinal magnetization
(b) Coil magnetization
(c) Central conductor magnetization
(d) None of the above
(d) None of the above
- Which of the following is false concerning a magnetic field in and around a hollow
conductor as compared to that of a solid conductor of the same outside diameter when
both are of the same magnetic material, and when the applied current is the same?
(a) The field immediately outside the outer surface of the hollow conductor is
greater
(b) The field gradient inside the hollow conductor is steeper
(c) The fields outside the conductors are the same
(d) The fields are the same at the centre
(c) The fields outside the conductors are the same
- The field in a section of ferromagnetic pipe being magnetized by means of a central
conductor is strongest at the:
(a) Ends of the pipe
(b) Outer surface of the pipe
(c) Inner surface of the pipe
(d) The field is uniform at all places
(c) Inner surface of the pipe
For a 7.6 cm (3 inches) diameter bar how much current is needed to magnetize the bar
for the detection of longitudinal discontinuities:
(a) 5500 amperes
(b) 16500 amperes
(c) 1000 amperes
(d) 3000 amperes
(d) 3000 amperes
- For detection of longitudinal discontinuities a 7.6 cm (3 inches) diameter bar is
magnetized in:
(a) The longitudinal direction
(b) The circular direction
(c) The clockwise direction
(d) None of the above directions
(b) The circular direction
- A bar that is 5 cm (2 inches) by 10 cm (4 inches) by 30.5 cm (12 inches) is being
magnetized in the circular direction. About how many amperes are required using the
perimeter approach?
(a) 2200
(b) 4500
(c) 3800
(d) None of the above
(c) 3800
- An advantage of AC is that:
(a) It is most readily available
(b) Equipment can be made lighter
(c) It leaves the part demagnetized
(d) All of the above
(a) It is most readily available
(b) Equipment can be made lighter
(c) It leaves the part demagnetized
(d) All of the above
- When a magnetic field cuts across a crack:
(a) Electrons begin jumping back and forth across the crack
(b) The crack begins to heat up
(c) Magnetic poles form at the edges of the crack
(d) All of the above
(c) Magnetic poles form at the edges of the crack
- A disadvantage of AC current is that it:
(a) Cannot be used with dry powder
(b) Has poor penetrating power
(c) Can only provide low flux densities
(d) Cannot be used for residual magnetic particle testing
(b) Has poor penetrating power
What causes a leakage field in a steel bar?
(a) A crack
(b) Reversal of the magnetic field
(c) Paint on the surface
(d) All of the above
(a) A crack
An indication is a defect under which of the following conditions?
(a) If it is greater than 3.8 cm (1.5 inches) long
(b) If it exceeds the limits of a standard or specification
(c) If it is deep
(d) Under all of the above indications
(b) If it exceeds the limits of a standard or specification
- A magnetic particle indication is sharp and very fine; this suggests that the
discontinuity is:
(a) Subsurface seam
(b) A shallow, tight surface crack
(c) Porosity
(d) A deep crack
(b) A shallow, tight surface crack
- Paint will not affect the detection of a crack if:
(a) The paint is thick and the defect is subsurface
(b) The paint is thin and the crack is parallel to the direction of flux lines
(c) The crack is sharp and the paint is thin
(d) All of the above
(c) The crack is sharp and the paint is thin
Among the following, the best type of current for the detection of fatigue cracks is:
(a) Half-wave direct current
(b) Alternating current
(c) Direct current
(d) Half-wave alternating current
(b) Alternating current
- Continuous magnetization provides the most sensitivity because:
(a) The magnetic particles are present while the part is being magnetized
(b) The magnetic field is greatest while the magnetizing current is on
(c) All of the above
(d) Neither of the above
(c) All of the above
- The sensitivity of magnetic particle testing is greatest when the discontinuity is:
(a) Parallel to the direction of the magnetic flux lines
(b) Perpendicular to the flow of the magnetizing current
(c) Perpendicular to the direction of the magnetic flux
(d) Perpendicular to the line between prods
(c) Perpendicular to the direction of the magnetic flux
- To provide reliability and reproducibility in magnetic particle testing, written
procedures should include:
(a) Location of the coil and current for each magnetization
(b) Requirements for ammeter calibration
(c) Type and concentration of the particles
(d) All of the above
(a) Location of the coil and current for each magnetization
(b) Requirements for ammeter calibration
(c) Type and concentration of the particles
(d) All of the above