exam Flashcards
(141 cards)
1
Q
What is electrification?
A
it is the process of adding or removing electrons from a body.
2
Q
define electrostatic
A
electrostatic is the study of electric charges at rest or stationary
3
Q
What are the 5 parts of law of electro static?
A
Repulsion and attraction, Inversed square law, Distribution, movement, concentration
4
Q
what is inversed square law?
A
it states that the force between charges is proportional to the product of its force field and is inversed to the squared distance between them
5
Q
Distribution part to the law of electrostatic?
A
states that the electrons gather at the surface of the conductor due to their like charges, they don’t stay close to one another.
6
Q
What is movement part to the law of electrostatic?
A
it states that the electrons travel on the surfaces of the conductors, not through them. Nothing else moves except for the electrons
7
Q
what does the concentration part of the law of electrostatic state?
A
states that the electrons like to gather at the area where there is a greatest curvature.
8
Q
What is static discharge?
A
is when there is a difference in charges that is great enough that when the distance is decrease between them, the electrons will JUMP to the other opposite charge due to attraction laws.
9
Q
what happens when static discharges occur? how does it appear on the x ray?
A
When static discharge occurs, it releases a form of photon and an audible sound. It shows up like a branch like tree roots on x rays called the tree branch artifact.
10
Q
what is the definition of potential diff.?
A
it is the force or strength of electron flow
11
Q
what are other names or identifier for potential difference?
A
EMF, Volt
12
Q
how do you determine the strength of Potential diff?
A
where there is a great difference in the ends of charges. When one end is more negative than the other.
13
Q
What is volt?
A
it is defined as 1 joule of work done on 1 coulomb of charge (1volt=1joule/1coulomb)
14
Q
volt is defined as 1 joule of ____ ____ on 1 _____ of charge
A
work done, coulomb
15
Q
Current is flow of electrons through a ________
A
conductor.
16
Q
how is current measured?
A
it is measured by how many electric charged particles flow through a point in one second
17
Q
what is the unit of measurement for Current?
A
ampere
18
Q
Ampere consist of movement of ______ x 10 to the ____
A
6.24, to the 18th power/second
19
Q
what are the 3 types of current?
A
direct current, alternating c, and pulsating c
20
Q
What is resistance?
A
resistance is the amount of oppositions which the electrons encounter as they travel in an electric circuit
21
Q
what is a unit of measurement forresistance?
A
Ohm
22
Q
Ohm is defined as a resistance to the flow of current by a column of ____ _____ long with diameter of _ square meter at 0 degrees celsius
A
Mercury, 106.3 cm, 1
23
Q
what are the three essential requirements for a circuit?
A
Voltage, conductor, and resistance
24
Q
what is resistance depended on?
A
Type of material, dimension of material, and temperature
25
Describe the benefits of AC over DC
Alternating current has a sine curve, DC only has one curve. AC oscilliates and DC pulsates
26
Describe the features of series circuit.
series circuit is a circuit that only has one path for electric charges to flow. The components are connected, end to end. If there is a break, the circuit is now open and cannot work.
27
describe the characteristics of series circuit
1, the total voltage is the sum of all voltage across each resistors.
2. the current is the same through out the circuit.
3. the total resistance is the sum of all resistors on the board.
28
what are the features of parallel circuit?
it has more than one path of current to flow. The parts are branches of main circuit. A break in circuit doesnot interrupt the flow.
29
What are the characteristics of the parallel circuit?
1. the voltage is the same throughout the circuit board
2. the current total is the sum of all currents at each current element.
3. resistors total is the reciprocal of all resistors on the board. 1/rt= 1/r1+1/r2
30
how do you define power?
it is the sum of power consumed or dissipated by each resistor or load.
31
how do you describe an electric generator?
it is a generator that can convert mechanical movement to electrical energy using faraday's law. It is moving flux lines in relationship to conductor to induce current.
32
what are the components of generator?
A generator has magnets, armature, slip rings, and stationary brushes.
33
what is the fxn of an armature in the generator?
it has a conductor. it is placed between two magnets to cut the lines of force between them.
34
what is the fxn of slip ring?
it is two metallic rings isolated from one another. they rotate with each armature, separately.
35
what is the fxn of stationary brushes?
They conduct current from armature and transmit it to the external circuit.
36
in terms of armature position, when is 0 energy produced and when is there peak energy produced?
when the armature is at 0 degrees, no energy is produced. when armature is at 90 degrees, there is peak.
37
what is the ratio of cycle per second to Hz?
it is 1:1
38
in a single sine curve, which represents one phase of Alternating current, what is the average value of amplitude?
63.7%,which is mathematically, 0.637 times the peak value.
39
_____ used in radiography are expressed in peak values
kilovoltage
40
what is voltage ripple?
it is the drop in voltage. essentially shows AC with DC-like peak values. it reaches 0 after peak. voltage is not constant.
41
what are the advantages of AC over DC?
provides the changing magnetic field that induces voltage in the secondary coil, mutual induction.
there is less power loss in AC than DC (ability to step up or step down current during transmission)
42
how do you define a transformer?
transformer is a device that has the ability to transform electric current into higher or lower intensities.
43
Transformer is composed of _____
2 coils, one primary (input) and one secondary (output).
44
what is transformer law?
Vs/Vp = Ns/Np. Primary voltage is directly proportionalto the ratio of # of turns in secondary coil to number of turns in the primary coil.
45
can the power output be greater than the power input?
no it cannot.
46
how do you convert kilovolts to volt and milli amps to amp?
kilovolts to volt is x1000 or 10 to the power of 3, add three 0s to the right
milliamps to amp is /1000 or x10 to the negative 3, add/move decimals to the left.
47
what is an operation principle of transformer?
Current from AC primary coil passes through and induces secondary coil inducing the electrons.
secondary has different numbers of windings from the primary. it is designed this way.
48
what type of core is used by the x ray generators?
shell type transformer. but there are 4 types, air core, open core, closed core.
49
how many ways are transformer's power losses?
3. I squared R, eddy current, hysteresis.
50
describe I squared R power loss in transformer
it is also called copper loss. It is the inherent loss that occur due to resistance that exists in current flow.
51
how is I²R power loss mitigated?
increasing the size of the diameter of the conductor
52
what is Eddy current loss?
it is the current moving in opposite direction of what induces them. Which is Lenz's law. Any conducting material is subjected to to Eddy current loss.
53
how do you mitigate eddy current loss?
laminate the transformer core.
54
describe hysteresis loss
it happens because the energy is spent on magnetize, demagnatize, and remagnatize the core material. When you have to re orient (magnetize) poles, it causes energy. this wastes electrical power.
55
how do you mitigate hysteresis?
by laminating the core with silicon iron core.
56
Define rectification.
process by which alternating current is changed to pulsating direct current.
57
what is a rectifier?
it is an electronic device, that allows current to flow in only one direction.
58
what are the fxn of rectifiers?
allow electrons to flow in one direction and offer high resistance to movement in the other direction
59
why does x ray tube operate in a direct current?
it operates this way to prevent the chance of electrons flowing in an opposite direction (AC). it can result in malfunction of the machine.
60
what is Diode made up of?
it is made of semiconductor materials, normally Silicon.
61
how are semiconductors classed?
into two types, N-type or P-type..
62
Inside a Diode, where do electrons flow?
at the P-N junction.
63
Describe the characteristics of N-type semiconductors.
in N type semiconductor, the electrons are loosely bounds and are free to move about inside of here.
64
describe the characteristic of P-type semiconductor
The P type semiconductor have electron traps. These are positive traps are holes and can migrate inside the material.
65
there are two process that occur inside the Diode, what are they?
forward bias and reverse bias
66
describe the actions in forward bias.
electrons and holes approaches one another, allowing the current to flow across the p and n junction and towards the external circuit
67
describe the actions in reverse bias
the electrons and holes move away from one another. This increases the barrier voltage and prevents the current to cross the junction.
68
how does x ray tube serve as a diode?
in the first phase, the cathode sends electrons to anode. At this time, the anode is still positively charged. At the later phase, anode becomes negatively charged due to all the electrons it receives from the cathode. Cathode is now positively charged and anode is negatively charged.
69
why is it bad for x ray tube to serve as a diode?
1. it has low heat loading capacity
2. the electrons can potentially return back to cathode after the last half phase, due to the anode overheating from thermionic emission.
70
what is half wave rectification?
it is a one pulse rectifier. it essentially stop the negative cycle part of the AC. But It is now wasted. now the AC acts almost like the DC, only receiving one peak per cycle. it is inefficient, b/c the other half of the cycle is wasted.
71
what is self rectification?
when x ray tube act as tube/diode.
72
what is a full wave rectification?
it is more efficient at this point, the negative part of the phase is used, with the help of 4 rectifiers in a bridge circuit. however, if a single unit fail, it goes back to half-wave immediately, as it is now missing a way of receiving electrons.
73
what are the advantages of full wave rectification?
gives the ability to increase more output of radiographic equipment. gives larger exposure
74
what is the disadvantage of full wave rectification
it is still giving some low energy and still only one peak.
75
what happens when a full-wave becomes half? (very important)
can cause underexposure and drop in miliammeter reading that is half the normal value
76
describe a three phase power
it is a multiple voltage waveforms that are "superimposed" to one another. it maintains almost constant high voltage it never drops to zero.
77
what is wrong with single phase voltage waveform?
it has low penetrability.
78
When full wave rectification is applied to 3 phase current it produces _____ ____ ______
3ph 6pulse, 3 ph 12 pulse, high freq.
79
describe 3 phase 6 pulses.
Ripple of
voltage never drops below
and how much more energy than single phase
13-25%
75-87%
35%
80
describe 3 phase 12 pulse.
ripple of
voltage never drops below
and how much more energy than singlephase
4-10%
90-96%
40%
81
describe high freq. what does it change the incoming line from? is it full wave rectified? when it is applied to x-ray tube, how much % of the time is it providing peak kv? how much ripple?
it changes the incoming line from 60Hz to 6000Hz. it is full wave rectified. it is 10% effective of the time, and 3-4% ripple.
82
what are some of the advantages to 3 phase power?
1. less voltage ripple.
2. higher effective kV. produces even less low energy x ray.
3. it is more efficient
83
what are some protective devices?
Ground - the electric flows straight to earth
Fuses - breaks the circuit that melts when heated
Circuit Breakers - permits the breaking of the circuit before a dangerous temperature is reached.
84
what is an autotransformer used for?
used to control voltage. Usually on the lower voltage side of the x ray circuit.
85
Know the autotransformer law formula
vs/vp=number of tapped turns/number of primary turns
86
what voltage are the x ray machines operating at?
210-220 volts
87
how is x ray circuit divided?
into Main circuit and Filament circuit
88
Describe some features of Main circuit.
it modifies incoming line power. it boosts voltage to range that is enough to produce x ray. it allows the radiographer to adjust amperage, voltage, and length of exposure.
89
The main circuit is broken up in two portion. What are they?
Primary and secondary side.
90
Primary circuit is ____ voltage and Secondary is _____ voltage
low, high
91
In primary circuit, what does autotransformer do?
provides various amount of kilovoltages for the x-ray tube.
92
x-ray transformer primary coil is connected to _____ by the _____
Autotransformer, by the kV selector
93
why is the wire in primary coil large?
to handle the high amperage.
94
what does timer and x-ray exposure switch do?
controls the current to the primary coil. opens and closes primary circuit.
95
X-ray transformer secondary coil is a _____ voltage transformer. It is a ____ ___ transformer
high voltage. Step up.
96
X ray tube is a common connection of _____ and _____ circuit
secondary of main circuit and filament
97
what are some features of Filament Circuit?
it modifies incoming power from the autotransformer to produce the thermionic emission.
98
A filament transformer is a ____ ____ transformer. the voltage supplied to filament is _____ than the voltage supplied to the filament transformer. When stepping down, you _____ the voltage, but you _____ the amperage.
stepdown transformer. lower, decrease, increase
99
what does the external structure of x ray tubes have?
support structure, protective housing, and tube enclosure
100
what are the 3 main types of support structures
ceiling support, floor to ceiling support, C-arm support
101
what does protective housing do?
provides mechanical support for the tube
102
what are some features of the protective housing?
made of cast steel, can absorb unwanted photons, it is lined with lead for additional absorption
103
whatis the fxn of protective housing?
controls leakage and scatter radiation, protects xray tube, cools the tube,
104
leakage radiation must not exceed _______
100mR/hr at 1 meter
105
what is the metal enclosure commonly referred to as?
the tube.
106
what does the tube has inside? and what is the tube made up of?
cathode and anode, pyrex glass
107
how are off focused radiation produced?
they are photons that are not produced at the focal spot
108
usually off focus radiation is absorbed by the protective housing, but what can it cause when it is not?
causes ghosting of structures.
109
what is a filament?
part of the cathode that emits electrons
110
Focus cup is a metal that _____ around the _____
shroud, filament
111
what is a space charge?
electron cloud near the filament
112
target is a region on ____ struck by electrons that came from _____
anode, filament
113
what is filament made up of?
thoriated tungsten
114
what is the melting point for thoriated tungsten?
3410 Celsius
115
what is the size of a filament? diameter, width, and length
coil is 0.1-0.2mm in diameter, 1-2mm wide, 7-15mm long
116
In modern X ray machines, how many filaments do they have? are they equal length? when is one used and when is the other?
2, small is used when image detail is important, the larger is used when high heat exposures are needed.
117
Cathode is also known as the filament. what is the fxn of cathode?
gives off electrons in production of X ray.
118
what does thermionic emission mean?
cooking off electrons on the filament.
119
how much heat is needed for thermionic emission?
10 volts, 3-5 amps
120
where is focusing cup located? what are they made up of?
around the filament. molybdenum or nickel
121
what does effectiveness of focusing cup depend on?
size and shape, strength of its charge, filament size and shape, position of the filament within the cup.
122
where is stator located?
it is located in the protective housing, outside the tube
123
what does the stator do?
it is part of electromagnetic induction motor
124
what are other names of targets?
focal spot, focal point, and focal track
125
The actual focal spot is located on the anode, what is this area?
this area is where the electrons first come into contact with. From here is where the x-ray are actually produced.
126
what is effective focal spot?
This is path where the focal spot projected onto the patient and the image receptor
127
what is anode heel effect?
it is a delay in travels of the entire beam to reach the effective focal spot. While traveling downward towards the patient, the intensity of the ray is stronger on the cathode side than the anode.
128
what is line focus principle?
states that the size of effective focal spot is always smaller than the actual focal spot. The efs and afs get smaller in size as anode angle become smaller. less surface area for the electrons to make contact with anode.
129
what are the 3 purposes of anode?
provides a target surface for incoming electrons from cathode, takes the high voltage from cathode and put it back into the x ray generator circuitry, and conducts thermal energy.
130
how much percent of photon is actual x ray?
.6%, 99.4% is thermal
131
what is the greatest limitation of x ray production?
heat
132
what is rotating anode made of?
graphite disc, tungsten alloy, rhenium focal track.
133
what allows the anode to spin in the tube?
induction motor, the stator.
134
what is the rate of rotation for rotating anode?
3000-3600 rpm
135
what is the relationship between the angle of the anode and size of effective focal spot?
the higher the amount of electrons can hit the anode, the larger the effective focal spot. It all depends on the angle size of the anode. the larger the angle the bigger the effective focal spot.
136
what is the difference in radiation intensity across the useful beam of an xray?
45%, 120-75.
137
where is the strongest x ray beam intensity?
along the cathode end.
138
what is arcing?
luminous discharge of electricity across a gap in a circuit between electrodes. Common type of tube failure.
139
what is open filament?
when the wires become thing and eventually breaks.
140
what are some causes of tube failure?
when tungsten is used up on both side (cat and ano), breaking of filament, single excessive exposures
141
what determines the factors that affect the tube capacity?
type of voltage rectification, use of either sing-3 phase generators, the angle of the target (heel eff), the speed of anode rotation, and the focal spot size.
