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RT: 34 > Electromagnetics ch. 4 > Flashcards

Electromagnetics ch. 4 Flashcards

1
Q

What is the primary purpose of the x-ray imaging system?

A

To convert electric energy ( what comes out of the wall) to electromagnetic energy (photons)

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2
Q

Describe the conversion that takes place from Electric energy into electromagnetic energy (EM)

A
  • The electric is supplied to the system through the electric current
  • Conversion takes place in the Tube
  • Most electric energy is converted into heat
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3
Q

Why do x-ray rooms need to be cool in temperature?

A

-Because most of the electric energy is converted into heat during conversion.

When temperature in the unit becomes too high they can malfunction

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4
Q

Electric energy is often converted into which 4 types of energy?

A
  1. Mechanical energy
    - through an electric motor
  2. Thermal energy
    ex: toaster
  3. Chemical energy
    - ex. “jumping the car” electric charge restores the chemical energy in battery
  4. Electromagnetic energy (EM)
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5
Q

What is thermal energy?

A

Heat

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6
Q

____ is the study or science of stationary electric charges

A

Electrostatics

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7
Q

Define electrostatics

A

study or science of stationary electric charges

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8
Q

What are the smallest units of electricity

A
  1. Electrons
    &
    2.Protons
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9
Q

Electrons (-) travel in the ____ whereas protons are located in the ___

A
  1. Orbital shells

2. Nucleus

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10
Q

Most discussions concerning electric interactions involve ___ electrons

A

Negative

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11
Q

____ electrical charges refer to charges with less electrons in comparison

A

positive

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12
Q

If the atom had more electrons than protons it is considered

A

negatively charged

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13
Q

If the atom has more protons than electrons it is considered

A

positively charged

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14
Q

How is electrification created by

A
  1. contact
    -In an attempt to equalize
    2.Friction
    -transferring of e-
    3.Induction
    -process of electrical fields acting on one another w/o contact
    (what we use)
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15
Q

How does something become electrified

A

when it has too many or too few electrons

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16
Q

Of the 3 ways to create electrification, which one do we use in x-ray

A

Induction

-process of electrical fields acting on one another w/o contact

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17
Q

____ = weaker charge

___= strong negative charge

A
    • charge

2. - Charge

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18
Q

Why is the earth considered a neutral ground

A

Because it contains infinite + & - charges and is always willing to take on more e-

aka:

  • Electric ground
  • Ground potential
  • Zero potential
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19
Q

Define electrostatics

A

Study of stationary or resting electric charges

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20
Q

every particle with a charge contains an electric field that surrounds it and is directed:
____ from “positive” charges
_____ to “negative” charges

A
  1. Away

2. Inward

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21
Q

Describe the law of attraction

A
  1. Unlike charges attract
    2.Like charges repel
    = this level of attraction or repulsion= electrostatic force
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22
Q

Name the 4 main laws of electrostatics

A
  1. Attraction
  2. Coulomb’s law
  3. Distribution
  4. Concentration
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23
Q

Describe Columbs law

1/4 electrostatic laws

A

Columb= unit of charge

-The law defines the magnitude of electrostatic force

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24
Q

What is the relationship between electrostatic force and the product of electrostatic charges

A

=columb’s law

Directly proportional
& inversely proportional to a square of the distance between them

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25
Q

Describe Law # 3 of electrostatics

Distribution

A

Electric charge distribution is uniform throughout or on the surface

  • Conductors: on external surfaces
  • Non conductors:throughout
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26
Q

Describe law # 4 of electrostatics

Concentration

A

Electric charge of a conductor is concentrated along the sharpest curvature of the surface

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27
Q

What is potential energy

-What is it measured in

A

=stored energy

-Measured in Volts (V)

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28
Q

Due to the 4 electrostatic laws, all electric charges contain ______

A

potential energy

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29
Q

Define electrodynamics

A

Study of electric charges in motion

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30
Q

How do electric charges move?

modes of transportation

A
  1. Conductor
  2. Insulator
  3. Superconductor
  4. Semi-conductor
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31
Q

Describe conductors

A

Any substance in which electrons flow easily

EX: Copper & Aluminum, Water

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32
Q

Moving charges through a conductor is called?

A

electric current or electricity

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33
Q

Describe insulators

A

Material that does not allow for electron flow

EX:
Plastic, Rubber, Glass & Clay

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34
Q

Describe semiconductors

A

Materials that acts as both an insulator and conductor depending on conditions

Ex:
Silicon & germanium

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35
Q

Describe super conductors

A

No resistance to electron flow in cold temperatures
-Does not require potential energy
Ex: titanium & Niobium

36
Q

Ohm’s law does not hold true for ____

A

Superconductors

37
Q

In what state do all materials resist flow of electorns

A

Room temperature

38
Q

Term for electrons moving along a wire

A

Electric current

-Measured in amperes (A)

39
Q

Electric current is measured in ?

A

amperes (A)

40
Q

term for an electric conductor that is made into a closed path, and resistance to the flow is controlled by varying conductor diameter / using insulators

A

Electric circuit

41
Q

What increases resistance in a conductive wire

A

making wire gauge smaller or inserting circuitry elements

42
Q

Increasing electric resistance =

A

reduced electric current

43
Q

the number of electrons flowing in a circuit is the ___.

A

Ampere (A)

44
Q

Describe resistance

-What is it measured in?

A

-Reduces electric current

-Measured in Ohms
Ω

45
Q

____ describes the behavior of a current within the circuit ( resistance in a circuit)

A

Ohms law (Ω)

46
Q

What is the formula for Ohms law (Ω)

A

V=IR

  • V= potential difference in volts
  • I= electric current (A)
  • R= resistance
47
Q

Name the elements and functions of an electric circuit
slide 39
(Study symbols)

A
  1. Resistor:
    - Inhibits flow of electrons
  2. Battery:
    - Provides electric potential
  3. Capacitor:
    - Momentarily stores electric charge
  4. Transformer: Increases or decreases voltage by fixed amount (AC) only)
48
Q

What type of circuit consists of:

All circuit elements connected in a line along the same conductor

A

Series circuirs

49
Q

Which type of circuit consists of :

Individual branches occur off of each component

A

Parallel circuits

50
Q

Name the two types of Electric circuits

A
  1. Series circuit

2. Parallel circuit

51
Q

What are the 2 types of current

A

AC & DC

52
Q

Describe AC

A

Alternating current

-Electrons that oscillate back and forth

53
Q

Describe DC

A

Direct current

-Electrons that flow in 1 direction

54
Q

Electric power is measured in ?

-How many ____ does an x-ray unit require?

A

watts (W)

x-ray unites require 20 - 150kW

55
Q

What is the formula for power

A

P=IV

p= power (W)
I= Amperes (A)
V=Voltage (V)

56
Q

Any charged particle in motion creates a _____

A

Magnetic field

57
Q

Term for when electrons rotate on their axis is referred to?

A

Electron spin

58
Q

Describe the magnetic field

A
  • Closed loops that move with charged particles
  • It is perpendicular to the motion of the particle
  • Lines of magnetic field do not start of end as electric field lines do
  • Consists of north and south poles
59
Q

small magnet created by electron orbit is known as?

A

Magnetic dipole

60
Q

Term for when many atomic magnets with their dipoles become aligned

A

Magnetic domain

61
Q

Name the 3 types of magnets

A
  1. Naturally occurring (earth)
  2. Artificially induced permanent magnet ( horseshoe/compass)
  3. Electromagnets
62
Q

Strength of magnetic field is ____to electric current ran through the wire

A

proportional

63
Q

Magnets are classified according to their origin of ____

A

Magnetic property

64
Q

Why does the earth have a magnetic field

A

because it spins on its axis as it orbis the sun

65
Q

_____ determines the ease in which a material can be magnetized

A

Magnetic permeability

66
Q

Name the 4 types of magnetic states of matter

A
  1. Nonmagnetic
  2. Diamagnetic
  3. Paramagnetic
  4. Ferromagnetic
67
Q

Describe non magnetic

1/4 magnetic state of matter

A

-Unaffected by magnetic fields

EX: wood, glass

68
Q

describe Diamagnetic

A

-material that is weakly repelled from both poles of a magnetic field

Ex: water, plastic

69
Q

Describe paramagnetic

A

-Weakly attracted to both poles of a magnetic field

Ex: Gadolinium

70
Q

Describe Ferromagnetic

A
  • Can be strongly magnetized

- Iron, Nickel, Cobalt

71
Q

____ has high magnetic susceptibility and greatly increases the strength of the magnetic filed

A

Iron

72
Q

Name the laws of magnetism

A 
1. Magnetic poles
(every magnet has 2 poles , N & S)
2.Repulsion/Attraction
(Like poles repel & opposite poles attract)
3.Inverse square law
73
Q

Ferromagnetic can made into a magnet by:

A

Induction

74
Q

What is the unit for magnetic field strength

A

Tesla ( T)

75
Q

A coil of wire

A

Solenoid
- Running a current through this creates electrons in motion which induces a magnetic field

-Magnetic field concentrated at the center of the coil

76
Q

A charge in motion induces _____

A

a magnetic field

77
Q

True or false: a charge at rest produces no magnetic field

A

True

78
Q

____ is a current carrying coil of wire wrapped around an iron core which intensifies the induced magnetic field

A

Electromagnet

79
Q

Law that states in order to induce a current with the use of a magnetic field , the field can not be constant , it must be changing

A

Faraday’s Law

80
Q

Faraday determined 4 factors to define electromagnetic induction :

A

(VANS)

  1. Velocity = of magnetic field
  2. Angle = of conductor
  3. Number = of coils (turns) on conductor
  4. Strength = of magnetic field
81
Q

What are the types of motors used in x-ray tubes

A

Induction motors

-rotates the anode of the tube

82
Q

____ transforms electric potential and current into higher and lower intensity
(regulates current & Voltage)

A

Transformer

-Operates only with AC

83
Q

What does “Step up” mean in the transformer

A

Increases volts, decrease amps

84
Q

What does step down mean in transformers

A

Decreases volts, increases amps

85
Q

What are the 3 types of transformers

A

1.Closed-core
2. Autotransformer
3.Shell-type
(mostly used)

86
Q

What type of transformer is most currently used today

A

Shell type transfromer

87
Q

___ is universal ground for traveling electrons

A

Earth

RT: 34 (8 decks)

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