chapter 4- Electromagnetism Flashcards
1
Q
like charges repel
opposites attract
north pole and south pole
A
magnets
2
Q
o Force between two magnetic fields directly proportional to product
of their magnitudes and inversely proportional to square of
distance between them
A
Inverse Square Law
3
Q
magnets demonstrate :
A
polarity
4
Q
inverse square law applies to :
A
-magnetism
-electric field
-gravity
5
Q
A coiled, helix of wire carrying
an electrical current
A
Solenoid
6
Q
required components for electromagnetic induction
A
Requires an interaction between a conductor and a magnetic field
o Magnetic field
o Conductor
o Relative motion
7
Q
Two types of induction
A
-mutual induction
-self induction
8
Q
-two coils
-varying current supplied to primary coil
-induces current in secondary coil
-two coils are electrically insulated from each-other
A
mutual induction
9
Q
which induction requires step up and step down
A
mutual induction
10
Q
which induction is primary to secondary
A
mutual
11
Q
where is step down located
A
in the filament
12
Q
what happens to the amps when volts is increased
A
amps decreases
13
Q
what happens to voltage when mA is increased
A
voltage decreases
14
Q
always present in coils supplied with alternating current
A
self induction
15
Q
convert mechanical energy to electrical energy
A
generators
16
Q
can produce direct current or alternating current
A
generators
17
Q
components of generator
A
armature
magnets
slip rings
brushes
18
Q
autotransformer and alternating current is your:
A
self induction
19
Q
is alternating current rectified or uncertified
A
unrectified
full wave
20
Q
is direct current rectified or unrecitified
A
rectified
1/2 wave
21
Q
what is your source orgin for voltage
A
autotransformer
22
Q
helps deliver current
A
step down
23
Q
what design does the direct current generators use
A
a commutor ring design
24
Q
what design does the alternating current generators use
A
slip rings
25
what circuit do you add all the numbers
series
26
what circuit do you take the lowest number and cut it in half
parallel
27
when 1 thing isnt working, the whole thing is down
series circuit
28
when 1 thing isnt working, just that area/ part isnt working
parallel circuit
29
olms law
V=IR
v=voltage
I=current
R=resistance
30
what is your unit for current
amperage
31
where is your step up and step down
step up - primary to secondary
step down - filament
32
what happens to your voltage when your amps is increased in step down
Voltage decreases
33
where is your rectifier located
secondary
34
is step down your current or voltage
current
35
what is volts changed to in step up
volts to kilovolts
36
line voltage compensator
adjusts low/high voltage
37
what current is rectified and unrectified
AC- unrectified
DC- rectified
38
xray tube energy is converted to:
mechanical to electrical
39
* Most efficient type of electrical generation
* Employs an armature with three coils
* 120° apart
* Each phase of induced current is separated by 120°
Three phase generation
40
* Convert electrical to mechanical energy
* Similar components to generators
* Armature supplied with current
uses Fleming’s Left-Hand Motor Rule
Motors
41
Synchronous
Coils turn at same rate as
armature supplying
current
42
Asynchronous
Variable speed
43
what are the motor types
synchronous and asynchronus
44
what waves are least efficient to most efficient
-half wave
-full wave
-3phase, 6 pulse
-3phase, 12 pulse
- high frequency
45
what are the types of meters
ammeter
voltmeter
46
what meter:
Connected in series
Measures current flow
ammeter
47
what meter :
Connected in parallel
Measure potential difference between two points in circuit
48
what controls electrical current
* Transformers
* Autotransformers
* Capacitors
49
what wave has 1% loss
high frequency
50
how much loss is in 3 phase 12 pulse
4 percent
51
how much loss is in 3 phase 6 pulse
13 percent
52
how much loss is in half and full wave
100 percent
53
what wave is the third efficient
3 phase 6 pulse
54
motor components
-rotor
-stator windings
55
what happens to the voltage and amps in step up and step down
step up:
increase in volts, decrease in amps
Step down:
decrease in volts, increase in amps
56
electrical storage energy
capacitor
57
is voltage higher or lower in step up
higher voltage
58
is voltage higher or lower in step down
voltage is lower
59
voltage induced in secondary coil directly related to number of turns in secondary coil
transformer law
60
what is the relationship between voltage and amperage in transformer law
Induced voltage and amperage are inversely proportional
61
what is the most common and most efficient transformer type
shell type
62
transformer types
Air Core
Open Core
Closed Core
Shell type
63
what side is the low and high voltage at
low voltage- primary side
high voltage - secondary side
64
boiling off electrons
thermionic emission
65
need for rectification:
xray tube can only operate on direct current
66
process of alernating to direct current
rectifier
-full wave more efficient
67
two designs for autotransformer
o Primary and secondary coils connected in series
o Single coil on central core
68
three divisions for basic xray circuit
1. Low voltage circuit
2. High tension circuit
3. Filament circuit
69
* Accumulates and stores electrical charge
* Charged with DC voltage
* Unit of capacitance
capacitors
70
* Process of changing AC to DC
Rectification
71
* Primitive form of current rectification
* Performed by x-ray tube which acts as a diode device in the
circuit
* X-ray tube not designed to be a diode rectifier
* Produces a DC waveform that is 50% of full-wave rectification
* Very inefficient x-ray production and damaging to tube
self rectification
72
* Produces a DC waveform similar to self-rectification
* Employs single rectifier in circuit
* Protects x-ray tube from acting as a diode rectifier
o Protection is marginal
* Inefficient x-ray production
* Utilized in very inexpensive x-ray units
o Veterinary
o Podiatric
Half-Wave Rectification
73
Takes advantage of both phases of alternating current
* Provides only DC to x-ray tube
* Uses at least four rectifiers in a bridge rectification circuit
* Most efficient form of current for x-ray production
o All modern equipment is full-wave rectified
Full-Wave Rectification
74
Electrical process of liberating electrons from a wire filament
* Filament is heated to very high temperature, due to its resistance
o Filament is typically tungsten
* “Boiling off” electrons create an electron cloud around filament
* Principle of an incandescent light bulb
* Very important to x-ray tube design
thermionic emission
75
what current does the electrons flow in one direction
direct current
76
The flow of electrons in an electrical circuit
current
77
what current does the electrons move back and forth
Alternating current
78
what current does transformers use?
Alternating current
79
difference in charge
voltage
80
what current does step up and step down transformers function on
alternating current
81
what is the rectifier located in between
step up and xray tube
82
number of distinct wave cycles
phase
83
number of voltage pulses per cycle
pulse
84
number of pulses
frequency
85
where there is more turns on primary compared to secondary is it step down or step up
step up
86
what is the turns ratio
N(secondary) / N(primary)
87
first of three transformers in xray circuit
autotransformer
88
can increase or decrease voltage and amps
can be step up or step down
small changes
adjustable
autotransformer
89
An electrical component that inhibits the flow of current through a circuit
designed to reduce current flow through a circuit
decreases voltage
resistors
90
a unit of measure of the degree of resistance between two points of a conductor within a circuit
ohms
91
also referred to as intensity and measure of electrical current
amperage
92
provides electrical potential /power
voltage
93
the resistance of the particles to flow within a circuit
ohms
94
the force given to each particle to move
voltage
95
all parts or circuit elements are connected in a continous line
any break causes the circuit to fail
series
96
its current is able to flow beyond its continuous line , a break in parallel circuit still allows it to function
parallel circuit
97
change the voltage (polarity) in an electrical circuit
increase or decrease voltage
transformers
98
transformers have three parts:
iron core
primary coil (electricity in)
secondary coil (electricity out)
99
polarity of voltage rapidly changes back and forth
unrectified
100
electrons flowing in the reverse direction are blocked
rectified
101
which rectification is described :
the gap between pulses has no electron flow and the other wave is blocked
half wave rectification
102
which rectification is described :
all electrons flow in the same direction
back flowing electrons are not blocked (their polarity is changed so they flow in the same direction)
no gaps between pulses, but wave drops to 0
full wave rectification
103
work by self induction
do step up and step down
make only small changes
has only 1 coil around a single coil
autotransformer
