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Radt 1303 Physics > Chapter 4 Exam > Flashcards

Chapter 4 Exam Flashcards

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1
Q

difference in electric potential, energy in a circuit

A

volt

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2
Q

electrons flow in only one direction
ex: batteries

A

direct current (DC)

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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)

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4
Q

closed pathway composed of wires and circuit elements through which electricity may flow

A

electric circuit

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5
Q

which circuit do we use in x-ray?

A

series circuit

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6
Q

device that opens a circuit (breaks the pathway)

A

switch

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7
Q

device that can increase or decrease voltage by a predetermined amount

A

transformer

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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

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9
Q

part of the transformer that increases voltage

A

step-up

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10
Q

part of transformer that decreases voltage, turns it into milliamperage (mA), increases heat

A

step-down

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11
Q

devices that convert electrical energy to mechanical energy through electromagnetic energy

A

electric motors

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12
Q

what are the 3 parts of the x-ray circuit?

A

primary, secondary, filament

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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

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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

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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

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16
Q

electrons boiling off filament is called

A

thermionic emission

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17
Q

more x-rays being created on the cathode side

A

anode heel effect

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18
Q

if you increase kVp by ___ it is the same as doubling your mass

A

15% (rule)

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19
Q

true or false? photons and x-rays are the same thing

A

true

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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

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21
Q

the study of electric charges

A

electrostatics

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22
Q

what are electrical charges measured in?

A

coulombs

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23
Q

1 coulomb is equal to the electrical charge of _________ electrons

A

6.25 x 10^18

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24
Q

good conductors have a _____ number of free electrons and good insulators have ____ free electrons

A

large, few

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25
Q

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

A

coulomb’s law

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26
Q

law of electrostatics

A

like charges repel and unlike charges attract
only negative charges are free to move in solid containers
electrical charges reside externally

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27
Q

the study of electric charges in motion; what we think of as “electricity”

A

electrodynamics

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28
Q

the ability to do work because of a separation of charges; electrons will flow from abundance to deficiency

A

electric potential

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29
Q

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

A

electric potential

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30
Q

The ability to do work due to a separation of charges

A

electric potential (volt)

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31
Q

An expression of the flow of electrons in a conductor

A

current (ampere)

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32
Q

The property of an element in a circuit that resists or impedes the flow of electricity

A

resistance (ohm)

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33
Q

a volt is the ratio of _____ to _______

A

joules to coulombs
volt = joules/coulombs

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34
Q

For electric current to flow, the following must be
present:

A

A potential difference between two electrodes
A suitable medium through which it can travel

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35
Q

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

A

resistance (ohm Ω)

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36
Q

the potential difference (voltage) across the total circuit or any part of that circuit is equal to the current (amperes) multiplied by the resistance

A

ohms law
voltage = I (current) x R (resistance)

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37
Q

what are the 4 factors of resistance?

A
  1. the material
  2. length (increase length = increase resistance)
  3. cross-sectional diameter
  4. temperature
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38
Q

Materials with an abundance of free
electrons that allow a relatively free flow
of electricity

A

conductors

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39
Q

Materials made up of atoms with tightly bound electrons that do not conduct electricity well even when attracted by a potential difference

A

insulators

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40
Q

Materials that will conduct electricity but not as well as conductors and that will
insulate but not as well as insulators

A

semiconductors

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41
Q

a _____ (complete) pathway for electricity is required for electricity to flow

A

closed circuit

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42
Q

an ____ (broken) pathway, such as occurs when a switch is turned off

A

open circuit

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43
Q

circuit elements are wired along a single conductor

A

series circuit

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44
Q

circuit elements “bridge” or branch across a conductor

A

parallel circuit

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45
Q

Total voltage is equal to

A

total current x total resistance:
V(T) =I(T) x R(T)

46
Q

Resistance is equal to

A

the sum of the individual resistances:
R(T) = R(1) + R(2) + R(3)

47
Q

Current is equal throughout

A

throughout the circuit:
I(T) = I(1) = I(2) = I(3)

48
Q

Voltage is equal to

A

the sum of the individual voltages:
V(T) = V(1) + V(2) + V(3)

49
Q

Total resistance is inversely
proportional to

A

the sum of the reciprocals of each individual resistance: 1/R(T) = 1/R(1) + 1/R(2) + 1/R(3)

50
Q

Produces electrons through a chemical reaction, stores an electric charge long term, and provides an electric potential

A

battery

51
Q

temporarily stores an electric charge

A

capacitor

52
Q

A “one-way valve” device; allows electrons to flow in only one direction

A

diode

53
Q

Emergency devices that break or open the circuit if there is a sudden surge of electricity to the circuit or device

A

Protective devices (fuses, circuit breakers)

54
Q

Inhibits the flow of electrons, thereby precisely regulating the flow of electricity through that part of the circuit where it is placed.

A

Resistor (and rheostat)

55
Q

A device that opens a circuit
(breaks the pathway)

A

switch

56
Q

A device that can increase or
decrease voltage by a
predetermined amount

A

Transformer

57
Q

An object may be electrified in 3 ways:

A

friction, contact, induction

58
Q

a process of connecting the electrical device to the earth via a conductor, is a protective measure

A

grounding

59
Q

Any charged particle in
motion creates a _______ _____

A

magnetic field

60
Q

The magnetic field of a
charged particle in
motion is _________ to the motion of that particle

A

perpendicular

61
Q

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.

A

flux

62
Q

The strength of the
magnetic field is measured in the

A

SI unit Tesla (T)

63
Q

who first identified the
principle of electromagnetism?

A

Hans Oersted

64
Q

who found that moving a conductor through a magnetic field induces an electric current in that conductor (called electromagnetic induction)?

A

Michael Faraday

65
Q

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

A

properties of electromagnets

66
Q

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

A

mutual induction

67
Q

an induced current flows in a direction that opposes the action (the changing magnetic field) that induced it

A

Lenz’s law

68
Q

Magnitude of induced electromagnetic force (emf) depends on 4 factors

A

Faraday’s law of electromagnetic induction

69
Q

what are the 4 factors of Faraday’s law of electromagnetic induction

A
  1. strength
  2. velocity
  3. angle
  4. # of turns
70
Q

Devices that convert some
form of mechanical energy
into electrical energy

A

electric generators

71
Q

Devices that convert electrical energy to
mechanical energy through electromagnetic
induction

A

electric motors

72
Q

transformer law for voltage:

A

V(s) / V(p) = N(s) / N(p)

(direct relationship)

73
Q

transformer law for current:
(inverse relationship)

A

I(s) / I(p) = N(p) / N(s)

74
Q

relation of voltage to current in a transformer:
(inverse relatioinship)

A

I(s) / I(p) = V(p)/ V(s)

75
Q

_______ and _______ transformers have a
ferromagnetic core to maximize efficiency

A

Closed-core, shell-type

76
Q

an on-off switch for the unit
connected to the facility’s power supply
(in primary circuit)

A

main power switch

77
Q

a device usually wired to the
autotransformer that automatically adjusts the power supplied to the x-ray machine to 220 volts
(in primary circuit)

A

line compensator

78
Q

protect against short circuits and electric shock
(in primary circuit)

A

circuit breakers

79
Q

an adjustable transformer
controlled by the kilovolt peak (kVp) selector on the
operating console
(in primary circuit)

A

autotransformer

80
Q

____ ______ _______ ensures consistent voltage to the x-ray tube and circuit (220 V AC)

A

line voltage compensator

81
Q

located in this section because it is easier to control (turn on and off)
a low voltage than a very high one

A

Timer circuit (exposure timer)

82
Q

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

A

Automatic exposure control (AEC) device

83
Q

It can “make” or
“break” the high
voltage across the
x-ray tube.
Most monitor mAS
for termination

A

guard timer (6s)

84
Q

a device placed in the secondary circuit that monitors x-ray tube current

A

mA meter

85
Q

what are the parts of the secondary circuit?

A

step-up transformer
rectification circuit
mA meter
x-ray tube

86
Q

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

A

rectifiers

87
Q

X-ray tubes must operate with _______ which will only allow e- flow from cathode (+) to anode (-). Otherwise, filament would be destroyed

A

direct current (DC)

88
Q

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

A

full wave rectification

89
Q

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

A

half-wave rectification

90
Q

Three waveforms can be phased or synchronized

A

alternating currents

91
Q

Three-phase, full-wave rectification
what % ripple?

A

13% to 3.5% ripple

92
Q

High-frequency, full-wave rectification
what % ripple?

A

< 1% ripple

93
Q

what are the parts of the filament circuit?

A

rheostat, exposure timer, step-down transformer

94
Q

fixed precision resistors that
reduce voltage to a value that = selected m

A

rheostats

95
Q

what are the parts/properties of the filament?

A

coil of tungsten wire
thermionic emission
space charge effect

96
Q

An x-ray tube is an example of current flow in a/an:

A

vaccum

97
Q

Which of the following increases or decreases voltage by a fixed amount?

A

transformer

98
Q

Which of the following is Coulomb’s law?

A

Electrostatic force between charges is directly proportional to product of quantities and inversely proportional to square of distance between them

99
Q

A rheostat will:

A

vary resistance

100
Q

In a metallic conductor:

A

Electrons move on external surface

101
Q

Nearly al discussion of electricity deals with the movement of:

A

Negative charges

102
Q

Which of the following conditions or environments will provide the least resistance?

A

Large cross-sectional area

103
Q

The potential difference that will maintain a current of 1 ampere in a circuit with a resistance of 1 ohm is the definition of:

A

Volt

104
Q

The removal of electrons from an object by rubbing it with another is electrification by:

A

Friction

105
Q

Which of the following allows electrons to flow in only one direction?

A

Diode

106
Q

Which of the following is a unit of measure of current?

A

Ampere

107
Q

Magnetic flux is:

A

Curved lines of force in space

108
Q

What is the magnetic classification of materials weakly attracted to magnets?

A

Paramagnetic

109
Q

The unit of measure for electric potential is:

A

V

110
Q

An ______ is an adjustable or variable form of resistor.

A

rheostat

Radt 1303 Physics (8 decks)

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