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Imaging Maintenance and Equipment > P Part III > Flashcards

P Part III Flashcards

1
Q

Fundamental property of some forms of matters
Has no smallest unit

A

Magnetism

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2
Q

T/F Any charged particle in motion creates a magnetic field

A

True

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3
Q

Property created when electrons behave as it rotate on its axis

A

Electron Spin

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4
Q

T/F Electron Spin neutralized in electron pairs [spins are oppositely directed] and creates a magnetic field

A

True

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5
Q

Any material that produce magnetic field

A

Magnetic

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6
Q

Magnets that have two poles

A

Bipolar/dipolar

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7
Q

The lines of a magnetic field are always [..]

A

Closed-loop

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8
Q

Small magnet created by the electron orbit

A

Magnetic Dipole

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9
Q

Explain MAGNETIC MOMENT

A

Nuclear magnetic dipole created when magnetic field is created by spinning electric charge
Collectively rotating subatomic particles create magnetic moment
[basis of MRI]

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10
Q

Explain MAGNETIC DOMAIN

A

Accumulation of many atomic magnets with their poles aligned
In Ferromagnetic material: randomly oriented

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11
Q

Ability of material to attract the lines of magnetic field intensity
Ex. Soft iron - high MP

A

Magnetic Permeability

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12
Q

Types of Magnets

A
  1. Naturally occurring magnets
  2. Artificially produced permanent magnets
  3. Electromagnets
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13
Q

Magnets are classified according to […] of the magnetic property

A

Origin

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14
Q

Magnets that get magnetism from the Earth

A

Naturally occurring magnets

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15
Q

Naturally occurring magnets [example]

A

Magnetite
o Oxide of iron (Fe3O4)
o Lodestone or leading stone

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16
Q

Magnets that get its magnetism induced artificially

A

Artificially produced permanent magnets

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17
Q

Artificially produced permanent magnets [example]

A

Compass
Bar of horse shoe shaped magnet

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18
Q

Coil of wire wrapped around an iron core that intensifies the magnetic field

A

Electromagnets

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19
Q

All matter can be classified to the [..]

A

Manner in which it interacts with the external magnetic field

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20
Q

Four magnets states of matter

A

Nonmagnetic
Diamagnetic
Paramagnetic
Ferromagnetic

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21
Q

Unaffected by magnetic field

A

Nonmagnetic

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22
Q

Nonmagnetic [example]

A

Wood and glass

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23
Q

Weakly repelled from both poles of magnetic field

A

Diamagnetic

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24
Q

Diamagnetic [example]

A

Copper 29, Water, Plastic

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25
Q

Weakly attracted to both poles of magnetic field

A

Paramagnetic

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26
Q

Paramagnetic [example]

A

Gadolinium [Gd-64]: contrast media in MRI

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27
Q

Strongly magnetized

A

Ferromagnetic

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28
Q

Ferromagnetic [example]

A

alnico (Al-12, Ni-28, Co-27) & iron (Fe-26)

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29
Q

Ability of a material to attract the lines of magnetic field intensity

A

Magnetic permeability

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30
Q

Degree which a material is magnetized

A

Magnetic susceptibility

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31
Q

Low susceptibility

A

Wood

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32
Q

High susceptibility

A

Iron

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33
Q

A condition wherein some materials that are susceptible are also reluctant to lose their magnetism [due to continuous magnetization of material]

A

Hysteresis Loss

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34
Q

Magnetically charged end of material
North and South [..]

A

Pole

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35
Q

Explain MAGNETIC LAWS

A

Like magnetic pole repels
Unlike magnetic pole attract
Imaginary lines of magnetic field enter South Poles
Imaginary lines of magnetic field leave the North Pole

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36
Q

Process of making ferromagnetic material magnet

A

Magnetic induction

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37
Q

Ferromagnetic objects can be made into magnets by

A

Induction [connect ferromagnets into a source ex. Battery, wire]

38
Q

Magnetic field strength
SI Unit: [..]
Older Unit: [..]

A

Tesla [T]
Gauss [G]
1 T = 10,000 G

39
Q

Study of physical interaction among electric charges, magnetic moments, electric fields

A

Electromagnetism

40
Q

[person, year] Observed that a dissected fro leg twitched with two different magnets

A

Luigi Galvani (1700s)

41
Q

Contributed on the development of battery

A

Alessandro Volta

42
Q

precursor of modern battery

A

Voltaic pile

43
Q

Voltaic pile composition

A

copper-zinc plates like a Dagwood sandwich

44
Q

Modern battery composition

A

carbon rod (+) & zinc
cylindrical can (-)

45
Q

Any device that converts some form of energy
directly into electric energy

A

Source of electromagnetic force

46
Q

[person, year] demonstrated that electric can be used to generate magnetic fields
Any charge in motion induces magnetic field

A

Hans Oersted (1820)

47
Q

Determines the direction of magnetic field

A

Right Hand Rule

48
Q

Explain RIGHT HAND RULE

A

If the right hand is wrapped around the wire so the thumb points in the direction of the current, the fingers will curl around the wire in the direction of the magnetic field

49
Q

Coil of wire

A

Solenoid

50
Q

A current carrying coil of wire wrapped around an iron core
It intensifies the induced magnetic field

A

Electromagnet

51
Q

Electromagnetic [advantage]

A

Magnetic field can be adjusted or turned on and off

52
Q

Observed the current in a current magnetic field
In changing of magnetic field, current is generated

A

Michael Faraday

53
Q

An electric current is induced in a circuit if some part of that circuit is in a changing magnetic field
Ex. Radio reception

A

Electromagnetic Induction

54
Q

Instrument to measure presence of electric current

A

Galvanometer

55
Q

Current produce during electromagnetic induction

A

Inducer current

56
Q

Four laws of electromagnetism

A

Faraday’s law of induction
Lenz’ law
Lorentz force
Ampere’s circuital flow

57
Q

[FARDAY’S LAW] The magnitude of the induced current depends on four factors:

A
  1. The strength of magnetic field
  2. The velocity of the magnetic field as it moves pass the conductor
  3. The angle of the conductor to the magnetic field
  4. The number of turns in the conductor
58
Q

Relationship of the magnitude of the induced current with the four factors

A
  1. The strength of magnetic field - PROPORTIONALITY
  2. The velocity of the magnetic field as it moves pass the conductor - PROPORTIONALITY
  3. The angle of the conductor to the magnetic field - INVERSELY
  4. The number of turns in the conductor - PROPORTIONALITY
59
Q

Factor 3. The angle of the conductor to the magnetic field; condition

A

90 degree relationship - IF CONDITION DOES NOT MOVE AT RIGHT ANGLES IN THE MAGNETIC FIELD THEN THERE IS REDUCED CURRENT

60
Q

Varying magnetic field intensity moves an [..]

A

Electric current

61
Q

Electromagnetic Devices

A

Electric Motor
Electric Generator
Transformer

62
Q

Electric current produces mechanical motion
Based on Oersted

A

Electric Motor

63
Q

Switches the direction of current through the loop

A

Commutator Ring

64
Q

Electron Motor [example]

A

Movement of needle of compass

65
Q

• A type of motor used with x-rays tubes
• It powers the rotating anode of an x-ray tube

A

Induction motor

66
Q

Mechanical motion produces electric current
Based on Faraday

A

Electric Generator

67
Q

It changes the intensity of alternating voltage & current
It works on AC only

A

Transformer

68
Q
A

DC

69
Q

Explain TRANSFORMER LAW

A

The change in voltage is directly proportional to the ratio of the number of turns (windings) in the secondary coil (Ns) to the number of turns in the primary coil (Np)

70
Q

Transformer Law Formula

A

Vs/Vp = Ns/Np

71
Q

Step -Up Transformer

A

• Turns ratio greater than 1
• Primary Side: low voltage, high current
• Secondary Side: high voltage, low current

72
Q

• Turns ratio less than 1
• Primary Side: high voltage, low current
• Secondary Side: low voltage, high current

A

Step-down transformer

73
Q

Transformer Law Effect on Current

A

A change in current & a change in voltage are inversely related

74
Q

Transformer Law Effect on Current Formula

A

Is/Ip = Np/Ns = Vp/Vs

75
Q

(3) ELECTRICAL POWER LOSSES IN TRANSFORMERS

A

Copper loss, Hysteresis Loss, Eddy current loss

76
Q

caused by the inherent resistance to current flow that is found in all conductors
Power lost is proportional to the square of the current

A

1^2R loss (Copper Loss)

77
Q

Reduce 1^2R loss (Copper Loss)

A

*Minimized by using low resistance wire
»large-diameter copper, and by using high voltage and low amperage

78
Q

Occurs because energy is expended as the continually changing AC current magnetizes, demagnetizes, and remagnetizes the core material.

»Demagnetization leaves some dipoles in the original orientation, and this residual magnetism causes the remagnetic effort to lag, thus producing more heat loss.

A

Hysteresis loss (lagging loss)

79
Q

The characteristic that requires energy to carry out this constant reorientation of the magnetic dipoles

A

coercivity

80
Q

Reduce Hysteresis loss (lagging loss)

A

Silicon iron

81
Q

result of currents opposing the cause that produced them
»They are produced in any conducting material subjected to changing magnetic fields.

A

Eddy current loss

82
Q

Reduce eddy current loss

A

-Laminating the transformer core reduces the eddy current loss by dividing the core into thin layers.

83
Q

Types of Transformer

A

Closed-core, Autotransformer & Shell-type

84
Q

A square core of ferromagnetic materials built up of laminated layers of iron

A

Closed-core transformer

85
Q

It helps to reduce energy losses caused by eddy current
Result: greater efficiency

A

Closed-core transformer

86
Q

A current that opposes the magnetic field that induced it, creating a loss of transformer efficiency

A

Eddy Current

87
Q

• It consists of one winding of wire & varies in
voltage & current by self-induction
• It is located in the operating console that
controls the kVp

A

Autotransformer

88
Q

It confines more of the magnet field lines of the primary winding

A

Shell-type transformer

89
Q

Rationale of shell-type transformer

A

the secondary is wrapped around it & there are essentially two closed cores

90
Q

Advantage of shell-type transformer

A

more efficient than closed-core transformer

Imaging Maintenance and Equipment (6 decks)

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