Chapter 4 Exam Flashcards
(110 cards)
1
Q
difference in electric potential, energy in a circuit
A
volt
2
Q
electrons flow in only one direction
ex: batteries
A
direct current (DC)
3
Q
electrons flow in one direction for the first half of the cycle and then in the other for the second half of the cycle
ex: U.S. current (60 Hz)
positive cycle: 1/120 second
A
alternating current (AC)
4
Q
closed pathway composed of wires and circuit elements through which electricity may flow
A
electric circuit
5
Q
which circuit do we use in x-ray?
A
series circuit
6
Q
device that opens a circuit (breaks the pathway)
A
switch
7
Q
device that can increase or decrease voltage by a predetermined amount
A
transformer
8
Q
Voltage goes back and forth
Operates on the principle of self-induction
Has only one coil of wire around a central magnetic core serving as both the primary and secondary coil
A
auto transformer
9
Q
part of the transformer that increases voltage
A
step-up
10
Q
part of transformer that decreases voltage, turns it into milliamperage (mA), increases heat
A
step-down
11
Q
devices that convert electrical energy to mechanical energy through electromagnetic energy
A
electric motors
12
Q
what are the 3 parts of the x-ray circuit?
A
primary, secondary, filament
13
Q
anode side, 220 volts come in and hit the switch which changes the volts to the same number as the set kVp (ex: 70 kVp = 70 volts), timer circuit, primary side of step-up transformer
A
primary circuit
14
Q
anode side, changes the number of volts to kilovolts (ex: 70 volts = 70 kilovolts), secondary side of step-up transformer, entire x-ray tube except for filament
A
secondary circuit
15
Q
cathode side, the mA meter, consists of rheostat, a step-down transformer and filaments, tiny coils of wire housed in the cathode of the x-ray tube
represented by the large and small focal spot
A
filament circuit
16
Q
electrons boiling off filament is called
A
thermionic emission
17
Q
more x-rays being created on the cathode side
A
anode heel effect
18
Q
if you increase kVp by ___ it is the same as doubling your mass
A
15% (rule)
19
Q
true or false? photons and x-rays are the same thing
A
true
20
Q
raising kVp creates higher quality x-ray photons which allows them to:
A
get through the 2.5mm aluminum equivalent filter where x-rays come out, instead of being trapped
21
Q
the study of electric charges
A
electrostatics
22
Q
what are electrical charges measured in?
A
coulombs
23
Q
1 coulomb is equal to the electrical charge of _________ electrons
A
6.25 x 10^18
24
Q
good conductors have a _____ number of free electrons and good insulators have ____ free electrons
A
large, few
25
The electrostatic force
between two charges is
directly proportional to the
product of their quantities and inversely proportional to the square of the distance between them
coulomb's law
26
law of electrostatics
like charges repel and unlike charges attract
only negative charges are free to move in solid containers
electrical charges reside externally
27
the study of electric charges in motion; what we think of as “electricity”
electrodynamics
28
the ability to do work because of a separation of charges; electrons will flow from abundance to deficiency
electric potential
29
Electrons bunched up on one end of a conductor creates an ______ ______ because the repulsive force causes some electrons to move so that work can be done
electric potential
30
The ability to do work due to a separation of charges
electric potential (volt)
31
An expression of the flow of electrons in a conductor
current (ampere)
32
The property of an element in a circuit that resists or impedes the flow of electricity
resistance (ohm)
33
a volt is the ratio of _____ to _______
joules to coulombs
volt = joules/coulombs
34
For electric current to flow, the following must be
present:
A potential difference between two electrodes
A suitable medium through which it can travel
35
The electrical resistance equal to the resistance between two points along a conductor that produces a current of 1 ampere when a potential difference of 1 volt is applied
resistance (ohm Ω)
36
the potential difference (voltage) across the total circuit or any part of that circuit is equal to the current (amperes) multiplied by the resistance
ohms law
voltage = I (current) x R (resistance)
37
what are the 4 factors of resistance?
1. the material
2. length (increase length = increase resistance)
3. cross-sectional diameter
4. temperature
38
Materials with an abundance of free
electrons that allow a relatively free flow
of electricity
conductors
39
Materials made up of atoms with tightly bound electrons that do not conduct electricity well even when attracted by a potential difference
insulators
40
Materials that will conduct electricity but not as well as conductors and that will
insulate but not as well as insulators
semiconductors
41
a _____ (complete) pathway for electricity is required for electricity to flow
closed circuit
42
an ____ (broken) pathway, such as occurs when a switch is turned off
open circuit
43
circuit elements are wired along a single conductor
series circuit
44
circuit elements “bridge” or branch across a conductor
parallel circuit
45
Total voltage is equal to
total current x total resistance:
V(T) =I(T) x R(T)
46
Resistance is equal to
the sum of the individual resistances:
R(T) = R(1) + R(2) + R(3)
47
Current is equal throughout
throughout the circuit:
I(T) = I(1) = I(2) = I(3)
48
Voltage is equal to
the sum of the individual voltages:
V(T) = V(1) + V(2) + V(3)
49
Total resistance is inversely
proportional to
the sum of the reciprocals of each individual resistance: 1/R(T) = 1/R(1) + 1/R(2) + 1/R(3)
50
Produces electrons through a chemical reaction, stores an electric charge long term, and provides an electric potential
battery
51
temporarily stores an electric charge
capacitor
52
A “one-way valve” device; allows electrons to flow in only one direction
diode
53
Emergency devices that break or open the circuit if there is a sudden surge of electricity to the circuit or device
Protective devices (fuses, circuit breakers)
54
Inhibits the flow of electrons, thereby precisely regulating the flow of electricity through that part of the circuit where it is placed.
Resistor (and rheostat)
55
A device that opens a circuit
(breaks the pathway)
switch
56
A device that can increase or
decrease voltage by a
predetermined amount
Transformer
57
An object may be electrified in 3 ways:
friction, contact, induction
58
a process of connecting the electrical device to the earth via a conductor, is a protective measure
grounding
59
Any charged particle in
motion creates a _______ _____
magnetic field
60
The magnetic field of a
charged particle in
motion is _________ to the motion of that particle
perpendicular
61
A magnetic field consists of lines of
force in space.
Lines of this travel from south pole to north pole inside the magnet and from north pole to south pole outside the magnet.
flux
62
The strength of the
magnetic field is measured in the
SI unit Tesla (T)
63
who first identified the
principle of electromagnetism?
Hans Oersted
64
who found that moving a conductor through a magnetic field induces an electric current in that conductor (called electromagnetic induction)?
Michael Faraday
65
Wire wrapped around iron
core
Electric current creates
magnetic field
Intensity of the field is
proportional to the electric
current
Iron core increases intensity
of the magnetic field lines
properties of electromagnets
66
What is it called when a moving
magnetic field (created by AC) is placed near a secondary coil, and
electricity is induced to flow in the secondary coil
mutual induction
67
an induced current flows in a direction that opposes the action (the changing magnetic field) that induced it
Lenz's law
68
Magnitude of induced electromagnetic force (emf) depends on 4 factors
Faraday's law of electromagnetic induction
69
what are the 4 factors of Faraday's law of electromagnetic induction
1. strength
2. velocity
3. angle
4. # of turns
70
Devices that convert some
form of mechanical energy
into electrical energy
electric generators
71
Devices that convert electrical energy to
mechanical energy through electromagnetic
induction
electric motors
72
transformer law for voltage:
V(s) / V(p) = N(s) / N(p)
(direct relationship)
73
transformer law for current:
(inverse relationship)
I(s) / I(p) = N(p) / N(s)
74
relation of voltage to current in a transformer:
(inverse relatioinship)
I(s) / I(p) = V(p)/ V(s)
75
_______ and _______ transformers have a
ferromagnetic core to maximize efficiency
Closed-core, shell-type
76
an on-off switch for the unit
connected to the facility’s power supply
(in primary circuit)
main power switch
77
a device usually wired to the
autotransformer that automatically adjusts the power supplied to the x-ray machine to 220 volts
(in primary circuit)
line compensator
78
protect against short circuits and electric shock
(in primary circuit)
circuit breakers
79
an adjustable transformer
controlled by the kilovolt peak (kVp) selector on the
operating console
(in primary circuit)
autotransformer
80
____ ______ _______ ensures consistent voltage to the x-ray tube and circuit (220 V AC)
line voltage compensator
81
located in this section because it is easier to control (turn on and off)
a low voltage than a very high one
Timer circuit (exposure timer)
82
Serves the same role as timer
Provide correct exposure regardless of patient size & reduce repeats
The patient’s body part of interest is the variable in determining when to terminate exposure
Uses a device called an ionization chamber
Three ion chambers placed between the patient and the image receptor
Automatic exposure control (AEC) device
83
It can “make” or
“break” the high
voltage across the
x-ray tube.
Most monitor mAS
for termination
guard timer (6s)
84
a device placed in the secondary circuit that monitors x-ray tube current
mA meter
85
what are the parts of the secondary circuit?
step-up transformer
rectification circuit
mA meter
x-ray tube
86
Solid state devices that allow
current to flow in only one
direction
converts AC to DC
occurs after the
step-up transformer and
before the x-ray tube
rectifiers
87
X-ray tubes must operate with _______ which will only allow e- flow from cathode (+) to anode (-). Otherwise, filament would be destroyed
direct current (DC)
88
Requires at least 4 diodes
Negative ½
reversed – anode always positive
2 diodes conduct during positive ½
2 diodes conduct during negative ½
Exposure time ½
full wave rectification
89
Rectifiers are arranged in pairs (0, 1, or 2 diodes)
One half of the AC cycle flows through the x-ray tube and the other half is suppressed (blocked)
Wastes ½ power & requires 2 x exposure
half-wave rectification
90
Three waveforms can be phased or synchronized
alternating currents
91
Three-phase, full-wave rectification
what % ripple?
13% to 3.5% ripple
92
High-frequency, full-wave rectification
what % ripple?
< 1% ripple
93
what are the parts of the filament circuit?
rheostat, exposure timer, step-down transformer
94
fixed precision resistors that
reduce voltage to a value that = selected m
rheostats
95
what are the parts/properties of the filament?
coil of tungsten wire
thermionic emission
space charge effect
96
An x-ray tube is an example of current flow in a/an:
vaccum
97
Which of the following increases or decreases voltage by a fixed amount?
transformer
98
Which of the following is Coulomb's law?
Electrostatic force between charges is directly proportional to product of quantities and inversely proportional to square of distance between them
99
A rheostat will:
vary resistance
100
In a metallic conductor:
Electrons move on external surface
101
Nearly al discussion of electricity deals with the movement of:
Negative charges
102
Which of the following conditions or environments will provide the least resistance?
Large cross-sectional area
103
The potential difference that will maintain a current of 1 ampere in a circuit with a resistance of 1 ohm is the definition of:
Volt
104
The removal of electrons from an object by rubbing it with another is electrification by:
Friction
105
Which of the following allows electrons to flow in only one direction?
Diode
106
Which of the following is a unit of measure of current?
Ampere
107
Magnetic flux is:
Curved lines of force in space
108
What is the magnetic classification of materials weakly attracted to magnets?
Paramagnetic
109
The unit of measure for electric potential is:
V
110
An ______ is an adjustable or variable form of resistor.
rheostat
