Physics - Exam Review Flashcards
The concept of removing an electron from an atom
Ionization
What are the two main categories of ionizing radiation?
Natural and man made
The velocity of light is constant and is symbolized by c
What is the value of c in m/s?
3x10^8 m/s
What is the unit of Radiation Absorbed Dose?
Gray (Gyt)
What is the smallest particle that has all the properties of an element?
Atom
What is the maximum number of electrons that can exist in the O shell?
2n^2
2(5)^2
= 50
Atomic nuclei that have the same atomic mass number but different atomic number?
Isobar
What are the two main types of particulate radiation?
Alpha and beta particles
Emission of particles and energy in order for an atom to become stable
Radioactivity
As frequency is increased, wavelength is _______
Decreased
Which diagnostic imaging modality is not part of the electromagnetic spectrum?
Ultrasound
Where do xray photons and gamma rays originate?
Gamma rays come from the nucleus
Xray photons come from the electron cloud
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
The study of stationary electric charges
Electrostatics
What are the ways in which electrification can occur?
Contact, friction, induction
What voltage is most commonly required for the operation of an xray imaging system
220V
Name the 4 different electrical classifications of materials
Conductor
Insulator
Semiconductor
Superconductor
An electric current can be induced if a circuit is placed in a ______ magnetic field
Varying
What are the 3 main components of the xray imaging system
Operating console, high voltage generator, xray tube
The operating console circuit is operated at _______ voltage
Low
What device stabilizes incoming voltage and adjusts it to precisely 220V?
Line compensator
The number of electrons emitted by the filament is determined by
The temperature of the filament
3 phase, 12 pulse waveform has what percentage of voltage ripple
4%
What are the 3 main types of xray tube support systems
Ceiling, floor to ceiling, c-arm
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?
AC
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?
2
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
