Physics - Exam Review Flashcards by Gracie Costello

The concept of removing an electron from an atom

Ionization

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What are the two main categories of ionizing radiation?

Natural and man made

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The velocity of light is constant and is symbolized by c
What is the value of c in m/s?

3x10^8 m/s

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What is the unit of Radiation Absorbed Dose?

Gray (Gyt)

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What is the smallest particle that has all the properties of an element?

Atom

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What is the maximum number of electrons that can exist in the O shell?

2n^2
2(5)^2
= 50

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Atomic nuclei that have the same atomic mass number but different atomic number?

Isobar

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What are the two main types of particulate radiation?

Alpha and beta particles

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Emission of particles and energy in order for an atom to become stable

Radioactivity

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As frequency is increased, wavelength is _______

Decreased

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Which diagnostic imaging modality is not part of the electromagnetic spectrum?

Ultrasound

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Where do xray photons and gamma rays originate?

Gamma rays come from the nucleus
Xray photons come from the electron cloud

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Decreasing the distance from an xray source by half will have what impact on the intensity of the beam?

Will increase the intensity of the beam by a factor of 4

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The study of stationary electric charges

Electrostatics

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What are the ways in which electrification can occur?

Contact, friction, induction

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What voltage is most commonly required for the operation of an xray imaging system

220V

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Name the 4 different electrical classifications of materials

Conductor
Insulator
Semiconductor
Superconductor

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An electric current can be induced if a circuit is placed in a ______ magnetic field

Varying

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What are the 3 main components of the xray imaging system

Operating console, high voltage generator, xray tube

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The operating console circuit is operated at _______ voltage

Low

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What device stabilizes incoming voltage and adjusts it to precisely 220V?

Line compensator

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The number of electrons emitted by the filament is determined by

The temperature of the filament

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3 phase, 12 pulse waveform has what percentage of voltage ripple

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What are the 3 main types of xray tube support systems

Ceiling, floor to ceiling, c-arm

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What type of xray tube support is most frequently used?

Ceiling support

What is the most common cause of abrupt tube failure

Electron Arching from the filament to the enclosure because of vaporized tungsten

As the target angle decreases, the effective focal spot size _______

Decreases

Xray quantity is directly proportional to _______

mAs

Xray quantity is inversely proportional to

Square of the Distance?

The autotransformer has only one ________

Coil

Line compensation accomplishes _______________

Is required to stabilize voltage

The filament transformer is usually __________

A step down transformer

The filament circuit operates on currents ranging from _______

3-6A Primary windings - 0.5-1A Secondary windings - 5-8A

What are the 4 types of timing circuits

Synchronous Electronic mAs AEC

High voltage transformers only operate on what type of current?

What are the 2 types of semiconductors used to form rectifiers?

N and P type

High frequency generators have what percentage of voltage ripple?

Less than 1%

What type of xray tube enclosures are less prone to arching?

Metal

Where is the ionization chamber positioned in a system using AEC

Between the IR and the patient

What are the 2 principal components of the cathode?

Filament and focusing cup

The release of electrons from a heated filament refers to?

Thermionic emission

What are the main functions of the anode?

Conducts electricity Radiates heat Radiates X-rays

Where is the power supplied to the xray imaging system firsts delivered?

Autotransformer

What is the major difference between the autotransformer and the conventional transformer?

Autotransformer has only one coil

Of all the different types of exposure timers, which one is the most accurate?

Electronic

What primarily determines the quality of the xray beam?

Kvp

mAs timers are located on what side of the high voltage transformer?

Secondary side

The product of xray tube current (mA) and exposure time (s) is mAs, but can also be referred to as ?

Electrostatic charge (C)

What are the 3 primary parts of the high voltage generator?

High voltage transformer Filament transformer Rectifiers

What is the purpose of the high voltage generator in xray imaging systems?

Increasing the output voltage from the autotransformer to the kvp necessary for xray production

The oil found inside the high voltage generator is used primarily for?

Electrical insulation

The only difference between the primary and secondary waveforms in high voltage transformers is their?

Amplitude

The process of converting AC to DC is referred to as?

Rectification

Why is voltage rectification required?

To ensure that electrons flow from xray tube cathode to anode

Rectification is accomplished through the use of what?

Diodes

Half wave rectified circuits contain how many diodes?

0-2 And 1/60s

What are 2 disadvantages of half wave rectification?

Half the power supply is wasted Requires twice the exposure time

What is the negative side of the xray tube?

Cathode

What is the approximate length of the filament?

1-2cm

Full wave rectified imaging systems contain at least how many diodes?

At least 4 diodes And 1/120s

How many cray pulses per second do full wave rectified, single phase xray units provide?

120

Which direction are X-rays emitted?

Isotropically

Xrays are emitted through a special section of the xray tube called the?

Window

What is the purpose of the protective housing of the xray tube?

Guards against excessive radiation exposure and electric shock

What are the 2 purposes of the oil found in the protective housing of the tube?

Insulator against electric shock and a thermal cushion to dissipate heat

Filaments are usually made of what material?

Thoriated tungsten

What is the approximate length of the xray tube?

30-50cm

What is the approximate size of the tube window?

5cm^2

What is the most common cause of tube failure?

Tungsten vaporization

The effectiveness of the focusing cup is determined by?

Its shape and size and its charge

Most rotating anode xray tubes have how many filaments?

The xray tube current is adjusted by controlling what?

The filament current

At any given filament current, the xray tube current rises with increasing voltage to a maximum value. A further increase in kvp does not result in a higher mA because all of the available electrons have been used. This is known as as?

Saturation current

The size of the small focal spot ranges from?

0.1-1mm

The size of large focal spots range from?

0.3-2mm

The positive side of the xray tube is the?

Anode

What are the 2 types of anodes?

Stationary and rotating

Stationary anode tubes are generally used for what type of diagnostic imaging systems?

Where high tube current and power are not required Ex. Dentist

Why do general purpose xray systems use rotating anodes?

They are capable of producing high intensity xray beams in a short time

What is the area of the anode that is struck by the electrons from the cathode?

Target

What type of motor is used to turn the anode?

Electromagnetic Induction motor

Where is the actual xray source?

Focal spot

What effect does angling the target have on the effective focal spot?

Smaller angle = smaller effective focal spot

The smaller the anode angle, the ___________ the heel effect

Larger

The heel effect results in less radiation intensity on what side of the xray beam?

Anode

What are the 3 ways in which heat can be dissipated in the xray tube?

Radiation, conduction, convection

The thermal capacity of an anode, and its heat dissipation characteristics are contained in a rating chart called?

Anode cooling chart

What is kinetic energy?

The energy associated with the motion of an object

The external magnetic field is supplied to induction motors by several fixed electromagnets called?

Stator

What device changes the intensity of alternating voltage and current?

Transformer

Define a step up transformer

A transformer with a turns ratio greater than 1, because voltage is increased or stepped up from primary to secondary

When emitted from the filament, electrons are on the vicinity of the filament before they are accelerated to the anode. Because these electrons carry negative charges, they repel one another and tend to form a cloud around the filament. This cloud is referred to as?

Space charge effect