P Part III Flashcards
1
Q
Fundamental property of some forms of matters
Has no smallest unit
A
Magnetism
2
Q
T/F Any charged particle in motion creates a magnetic field
A
True
3
Q
Property created when electrons behave as it rotate on its axis
A
Electron Spin
4
Q
T/F Electron Spin neutralized in electron pairs [spins are oppositely directed] and creates a magnetic field
A
True
5
Q
Any material that produce magnetic field
A
Magnetic
6
Q
Magnets that have two poles
A
Bipolar/dipolar
7
Q
The lines of a magnetic field are always [..]
A
Closed-loop
8
Q
Small magnet created by the electron orbit
A
Magnetic Dipole
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]
10
Q
Explain MAGNETIC DOMAIN
A
Accumulation of many atomic magnets with their poles aligned
In Ferromagnetic material: randomly oriented
11
Q
Types of Magnets
A
- Naturally occurring magnets
- Artificially produced permanent magnets
- Electromagnets
12
Q
Magnets are classified according to […] of the magnetic property
A
Origin
13
Q
Magnets that get magnetism from the Earth
A
Naturally occurring magnets
14
Q
Naturally occurring magnets [example]
A
Magnetite
o Oxide of iron (Fe3O4)
o Lodestone or leading stone
15
Q
Magnets that get its magnetism induced artificially
A
Artificially produced permanent magnets
16
Q
Artificially produced permanent magnets [example]
A
Compass
Bar of horse shoe shaped magnet
17
Q
Coil of wire wrapped around an iron core that intensifies the magnetic field
A
Electromagnets
18
Q
All matter can be classified to the [..]
A
Manner in which it interacts with the external magnetic field
19
Q
Four magnets states of matter
A
Nonmagnetic
Diamagnetic
Paramagnetic
Ferromagnetic
20
Q
Unaffected by magnetic field
A
Nonmagnetic
21
Q
Nonmagnetic [example]
A
Wood and glass
22
Q
Weakly repelled from both poles of magnetic field
A
Diamagnetic
23
Q
Diamagnetic [example]
A
Copper 29, Water, Plastic
24
Q
Weakly attracted to both poles of magnetic field
A
Paramagnetic
25
Paramagnetic [example]
Gadolinium [Gd-64]: contrast media in MRI
26
Strongly magnetized
Ferromagnetic
27
Ferromagnetic [example]
alnico (Al-13, Ni-28, Co-27) & iron (Fe-26)
28
Ability of a material to attract the lines of magnetic field intensity
Magnetic permeability
29
Degree which a material is magnetized
Magnetic susceptibility
30
Low susceptibility
Wood
31
High susceptibility
Iron
32
A condition wherein some materials that are susceptible are also reluctant to lose their magnetism [due to continuous magnetization of material]
Hysteresis Loss
33
Magnetically charged end of material
North and South [..]
Pole
34
Explain MAGNETIC LAWS
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
35
Process of making ferromagnetic material magnet
Magnetic induction
36
Ferromagnetic objects can be made into magnets by
Induction [connect ferromagnets into a source ex. Battery, wire]
37
Magnetic field strength
SI Unit: [..]
Older Unit: [..]
Tesla [T]
Gauss [G]
1 T = 10,000 G
38
Study of physical interaction among electric charges, magnetic moments, electric fields
Electromagnetism
39
[person, year] Observed that a dissected fro leg twitched with two different magnets
Luigi Galvani (1700s)
40
Contributed on the development of battery
Alessandro Volta
41
precursor of modern battery
Voltaic pile
42
Voltaic pile composition
copper-zinc plates like a Dagwood sandwich
43
Modern battery composition
carbon rod (+) & zinc
cylindrical can (-)
44
Any device that converts some form of energy
directly into electric energy
Source of electromagnetic force
45
[person, year] demonstrated that electric can be used to generate magnetic fields
Any charge in motion induces magnetic field
Hans Oersted (1820)
46
Determines the direction of magnetic field
Right Hand Rule
47
Explain RIGHT HAND RULE
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
48
Coil of wire
Solenoid
49
A current carrying coil of wire wrapped around an iron core
It intensifies the induced magnetic field
Electromagnet
50
Electromagnets [advantage]
Magnetic field can be adjusted or turned on and off
51
Observed the current in a current magnetic field
In changing of magnetic field, current is generated
Michael Faraday
52
An electric current is induced in a circuit if some part of that circuit is in a changing magnetic field
Ex. Radio reception
Electromagnetic Induction
53
Instrument to measure presence of electric current
Galvanometer
54
Current produce during electromagnetic induction
Inducer current
55
Four laws of electromagnetism
Faraday’s law of induction
Lenz’ law
Lorentz force
Ampere’s circuital flow
56
[FARDAY’S LAW] The magnitude of the induced current depends on four factors:
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
57
Relationship of the magnitude of the induced current with the four factors
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
58
Factor 3. The angle of the conductor to the magnetic field; condition
90 degree relationship - IF CONDITION DOES NOT MOVE AT RIGHT ANGLES IN THE MAGNETIC FIELD THEN THERE IS REDUCED CURRENT
59
Varying magnetic field intensity moves an [..]
Electric current
60
Electromagnetic Devices
Electric Motor
Electric Generator
Transformer
61
Electric current produces mechanical motion
Based on Oersted
Electric Motor
62
Switches the direction of current through the loop
Commutator Ring
63
Electron Motor [example]
Movement of needle of compass
64
• A type of motor used with x-rays tubes
• It powers the rotating anode of an x-ray tube
Induction motor
65
Mechanical motion produces electric current
Based on Faraday
Electric Generator
66
It changes the intensity of alternating voltage & current
It works on AC only
Transformer
67
Explain TRANSFORMER LAW
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)
68
Transformer Law Formula
Vs/Vp = Ns/Np
69
Step -Up Transformer
• Turns ratio greater than 1
• Primary Side: low voltage, high current
• Secondary Side: high voltage, low current
70
• Turns ratio less than 1
• Primary Side: high voltage, low current
• Secondary Side: low voltage, high current
Step-down transformer
71
Transformer Law Effect on Current
A change in current & a change in voltage are inversely related
72
Transformer Law Effect on Current Formula
Is/Ip = Np/Ns = Vp/Vs
73
(3) ELECTRICAL POWER LOSSES IN TRANSFORMERS
Copper loss, Hysteresis Loss, Eddy current loss
74
caused by the inherent resistance to current flow that is found in all conductors
Power lost is proportional to the square of the current
1^2R loss (Copper Loss)
75
Reduce 1^2R loss (Copper Loss)
*Minimized by using low resistance wire
»large-diameter copper, and by using high voltage and low amperage
76
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.
Hysteresis loss (lagging loss)
77
The characteristic that requires energy to carry out this constant reorientation of the magnetic dipoles
coercivity
78
Reduce Hysteresis loss (lagging loss)
Silicon iron
79
result of currents opposing the cause that produced them
»They are produced in any conducting material subjected to changing magnetic fields.
Eddy current loss
80
Reduce eddy current loss
-Laminating the transformer core reduces the eddy current loss by dividing the core into thin layers.
81
Types of Transformer
Closed-core, Autotransformer & Shell-type
82
A square core of ferromagnetic materials built up of laminated layers of iron
Closed-core transformer
83
It helps to reduce energy losses caused by eddy current
Result: greater efficiency
Closed-core transformer
84
A current that opposes the magnetic field that induced it, creating a loss of transformer efficiency
Eddy Current
85
• 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
Autotransformer
86
It confines more of the magnet field lines of the primary winding
Shell-type transformer
87
Rationale of shell-type transformer
the secondary is wrapped around it & there are essentially two closed cores
88
Advantage of shell-type transformer
more efficient than closed-core transformer
