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Chapter4 Flashcards

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1
Q

Is the study of stationary electric charges

A

Electrostatic

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2
Q

Study of electronic charges in motion

A

Electrodynamics

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3
Q

Electrical charge is measured in

A

Si unit, in coulomb 6.25 x 10^18

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4
Q

Good conductors have

A

Large numbers Free electrons

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5
Q

Good insulators have

A

Few free electrons

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6
Q

Example of good conductors

A

Cooper, water, and gold

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7
Q

Examples of good insulators

A

Glass plastic ceramic and wood

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8
Q

Five principles electrostatic: Like charges repel and unlike charges attract

A

the first principle

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9
Q

Five principles electrostatic: Electrostatic force between two charge is directly proportional to product of their quantities and inversely proportional to the square of distance

A

the second principle

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10
Q

Five principles electrostatic: Electric charges reside only on the external surface of a conductor

A

the third principle

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11
Q

Five principles electrostatic: The concentration of charge on a curved surface of a conductor is greatest where the curvature is greatest.

A

the fourth principle

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12
Q

Only negative charges are free to move in solid conductors

A

Five principles electrostatic: the fifth principle

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13
Q

In electrostatic, electfrication of objects occur when they gain a net positive or negative charge. True of false

A

True

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14
Q

Object may be Electricfied in 3 ways 

A

Friction, contact, induction

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15
Q

True or false for electric current to an electric potential must exist

Redo this one

A

True

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16
Q

An expression of the flow of electrons in a conductor.

A

Current

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17
Q

is measured in ampere

A

Current

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18
Q

Electron potential is measured in

A

Volts

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19
Q

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

A

Resistance

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20
Q

Resistance is measured in

A

Ohm

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21
Q

Volts is named after

A

Volta who invented the battery

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22
Q

Is the potential difference that will maintain a current of 1 ampere in a circuit with a resistance of 1 ohm

A

Volts

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23
Q

True or false volts is the expression of the difference in electric potential between two points

A

True

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24
Q

True or false Volts is also equal to the amount of work ( joules ) that can be done per unit of charge

A

True

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25
Q

Formula of volts

A

Volts = joules / coulombs

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26
Q

Is the peak kilo voltage and its selection represents the highest intensity of an X-ray photon possible for that setting

A

kVp

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27
Q

Amperes is named after

A

Andres Marie’s amperes, French physicist who made a significant contribution to the study of electrodynamics

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28
Q

Amperes is define as

A

1 coulomb flowing by given point in 1 second

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29
Q

For electric currents to flow there must be two things presents

A
  1. Potential difference between two electrodes
  2. Suitable medium through which it can travel
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30
Q

Are conductors and those resisting electric current flow are insulators

A

Suitable media

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31
Q

What two suitable medias

A

Vacuums and metallic conductors

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32
Q

Flows in one direction examples batteries

A

Direct current

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33
Q

Changes direction in cycles as the electric potential of source changes. Example electricity in homes in the u.s

A

Alternating current

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34
Q

Ohms is named after

A

Physicist georg Simon ohm who discovered the inverse relationship between current and resistance

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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

Ohm

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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
➢V = IR

A

Ohms law

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37
Q

V= i r

A

V- voltage
I - current
R- resistance

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38
Q

The amount of resistance in a conductor depends on four things:

A

Material
➢Length
➢Cross-sectional area
➢Temperature

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39
Q

allow free flow of current b|c they have an abundance of free electrons, when other materials have resistance b/c they do not have free electrons

A

Material

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40
Q

Resistance is directly proportional to the length of the conductor, a long conductor have more resistance than a short one

A

Length

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41
Q

Larger cross selections area Has a lower resistance than one with a small cross sectional area b/c greater external surface are which electrons can travel

A

Cross selections, arwa

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42
Q

Metallic conductors the resistance is greater as the temperature of conductors rises

A

Temperature

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43
Q

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

A

Conductors

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44
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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45
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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46
Q

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

A

Electric circuit

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47
Q

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

A

Close circuit

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48
Q

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

A

Open circuit

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49
Q

circuit elements are wired along a single conductor

A

Series circuit:

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50
Q

circuit elements “bridge” or branch across a conductor

A

Parallel circuit:

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51
Q

Is a complex version that has different voltage and current flowing through different sections

A

X-ray circuit

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52
Q

There are 7 electronic devices

A

Battery
➢Capacitor
➢Diode
➢Protective devices (fuses and circuit breakers)
➢Resistor or rheostat
➢Switch
➢Transformer

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53
Q

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

A

Battery

54
Q

Temporarily stores an electric charge and cannot produce new charges

A

Capacitor

55
Q

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

A

Diode

56
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)

57
Q

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

A

Resistor

58
Q

is simply an adjustable or variable form of resistor.

A

rheostat

59
Q

A device that opens a circuit (breaks the pathway)

A

Switch

60
Q

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

A

Transformer

61
Q

This is the process of connecting an electrical device to the earth via a conductor.

A

Grounding

62
Q

Any charged object can be_________ if it is grounded.

A

neutralized

63
Q

True or false Positively charged objects take on electrons from the earth, and negatively charged objects give up electrons to the earth until neutral.

A

True

64
Q

True or false When activated by a “live” wire, this “short circuit” into the ground wire trips the circuit breaker, shutting off the electricity to the circuit.

A

True

65
Q

The ability of a material to attract iron, cobalt, or nickel

A

Magnetism

66
Q

The nature of magnetic materials is that the orbital electrons of their atoms spin in predominately_________

A

One direction

67
Q

Atoms creat tiny magnetic called

A

Magnetic dipole

68
Q

True or false When dipoles or “atomic magnets” form groups of similarly aligned atoms, they create magnetic domains.

A

True

69
Q

A magnetic field consists of lines of force in space.

A

Flux

70
Q

Flux has 3 basic characteristics

A
  1. Lines of flux travel from south pole to north pole INSIDE the magnet and from north pole to south pole OUTSIDE the magnet.
  2. Lines of flux in the same direction repel each other and lines of flux in the opposite direction attract each other.
  3. Magnetic fields are distorted by magnetic materials and are unaffected by nonmagnetic materials.
71
Q

There are three laws of magnetism that may help explain electromagnetism:

A
  • Every magnet has a north and south pole.
    ➢Like poles repel each other and opposite poles attract each other.
    ➢The force of attraction or repulsion varies directly with the strength of the poles and inversely with the square of the distance between them.
72
Q

The strength of the magnetic field is measured in the SI unit

A

Tesla (T).

73
Q

Tesla is named after

A

American physicist nikola Tesla

74
Q

True or false Magnetic resonance imaging (MRI) units used for medical imaging are referred to by their magnetic field strength and operate with fields from 0.5 to 5 T.

A

True

75
Q

(e.g., glass, wood, plastic) are not attracted to magnetic fields at all

A

Nonmagnetic materials

76
Q

(e.g., water, mercury, gold) are weakly repelled by magnetic fields.

A

Diamagnetic materials

77
Q

(e.g., platinum, gadolinium, aluminum) are weakly attracted to magnetic fields.

A

Paramagnetic materials

78
Q

e.g., iron, cobalt, nickel) are strongly attracted to magnetic materials.

A

Ferromagnetic materials

79
Q

Electricity and magnetism are two parts of the same basic force.

A

Any flow of electrons, whether in space or in a conductor, will be surrounded by a magnetic field.
➢A moving magnetic field can create an electric current.

80
Q

First identified the principle of electromagnetism
➢Later, it was discovered that the magnetic field surrounding a conductor could be intensified by fashioning it into a coil (called a solenoid)

A

Hans Oersted

81
Q

Who Found that moving a conductor through a magnetic field induces an electric current in that conductor (called electromagnetic induction).

A

Michael Faraday

82
Q

The induction of electricity in a secondary coil by a moving magnetic field. When a moving magnetic field is placed near a secondary coil, electricity is induced to flow in that coil

A

Mutual induction

83
Q

Requires an understanding of Lenz’s law, which states that an induced current flows in a direction that opposes the action (the changing magnetic field) that induced it

A

•Self-induction

84
Q

is created in a coil carrying electrical current and expands outward from the center of the coil

A

A magnetic field

85
Q

Devices that convert some form of mechanical energy into electrical energy

A

Electric generators

86
Q

Devices that convert electrical energy to mechanical energy through electromagnetic induction

A

Electric motors

87
Q

Devices used to increase or decrease voltage (or current) through electromagnetic induction

A

Transformers

88
Q

increases voltage.

A

A step-up transformer

89
Q

decreases voltage.

A

step-down transformer

90
Q

Transformer law for voltage:

A

Vs / Vp = Ns / Np (direct relationship)

91
Q

Transformer law for current:

A

Is / Ip = Np / Ns (inverse relationship)

92
Q

Relation of voltage to current in a transformer:

A

Is / Ip = Vp / Vs (inverse relationship)

93
Q

True or false Closed-core and shell-type transformers have a ferromagnetic core to maximize efficiency.

A

True

94
Q

Adjustable transformer controlled by Kvp selector on the operating console. Operates on the principle of self-induction and Has only one coil of wire around a central magnetic core serving as both the primary and secondary coil

A

Autotransformer

95
Q

Consists of the main power switch, circuit breakers, the autotransformer, the timer circuit, and the primary side of the step-up transformer

A

Primary circuit

96
Q

Consists of the secondary side of the step-up transformer, the mA meter, a rectifier bank, and the x-ray tube (except for the filaments)

A

Secondary circuit

97
Q

Consists of a rheostat, a step-down transformer, and the filaments

A

Filament circuit

98
Q

an on-off switch for the unit connected to the facility’s power supply

A

Main power switch

99
Q

a device usually wired to the autotransformer that automatically adjusts the power supplied to the x-ray machine to 220 volts

A

Line compensator:

100
Q

protect against short circuits and electric shock

A

Circuit breakers

101
Q

used to increase the voltage from the autotransformer to the kilovoltage necessary for x-ray production

A

Step-up transformer:

102
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)

103
Q

Serves the same role as timer. The patient’s body part of interest is the variable in determining when to terminate exposure
•Uses a device called an ionization chamber

A

Automatic exposure control (AEC) device

104
Q

begins with the rest of the step-up transformer

A

The secondary circuit

105
Q

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

A

mA meter

106
Q

needed to convert AC to DC and are arranged in pairs

A

Rectifiers

107
Q

One half of the AC cycle flows through the x-ray tube and the other half is suppressed (blocked).

A

Half-wave rectification

108
Q

Single-phase, full-wave power

A

100 ripples

109
Q

Three-phase, full-wave rectification

A

13% to 3.5% ripple

110
Q

Alternating currents

A

Three waveforms can be phased or synchronized

111
Q

High-frequency, full-wave rectification

A

< 1% ripple

112
Q

True or false Rectifiers—the one-way valves—are necessary to route the electricity through the x-ray tube correctly

A

True

113
Q

For a filament circuit, a variable resistor controlled by the mA selector on the operating console

A

Rheostat

114
Q

works in concert with the rheostat; together, they determine the quantity of electrons boiled off of the filament and available for x-ray production. ( filament circuit)

A

Exposure timer

115
Q

used in the filament circuit to increase the current by reducing the voltage that is applied to the filament

A

Step-down transformer

116
Q

Tiny coils of wire housed in the cathode of the x-ray tube
➢Represented on the operating console by the “large focal spot” and “small focal spot”

A

Filament

117
Q

The quantity is controlled by a_______to reflect the mA selected on the control console.

A

rheostat

118
Q

Now we can join the two halves of the process:

A

We have a group, or cloud, of electrons created by the filament circuit (heating of the filament).
➢The kilovoltage applied to the x-ray tube created a large positive charge on the anode and a large negative charge on the cathode (focusing cup).

119
Q

True or false The large positive charge attracts the electrons boiled off the filament, giving them tremendous kinetic energy in the process.

A

True

120
Q

True or false The large negative charge on the cathode keeps the electrons crowded together; otherwise, they would repel each other and scatter throughout the tube.

A

True

121
Q

True or false The electrons travel across to the anode and interact there to produce x-rays until the timer circuit terminates the process.

A

True

122
Q

Is the property of an element in a circuit that resist or impedes the flow of electricity

A

Resistance

123
Q

The unit of measured

A
124
Q

A type of current that flows in only one direction.

A

Direct current

125
Q

A battery a example of a direct current because

A

It has a positive and negative electrodes and when placed in an electrical circuit electrons flow from the negative terminal to the positive terminal

126
Q

In the u.s the Electricity flows into homes alternates at 60 cycles per seconds. Expressed as 

A

Frequency of 60Hz

127
Q

Examples of good semi conductors

A

Germanium diamond and silicon

128
Q

A section of special wires usually in case in glass that quickly melts if the Current flow rises excessively thus opening the circuit

A

Fuse

129
Q

As voltage increases the current

A

Decreases

130
Q

X ray Circuits are divided into three circuits

A

Primary secondary and filaments

131
Q

Milliampere parameter

A

Tube current

Rad Physics (4 decks)

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