physics Flashcards
matter
anything that occupies space and has shape or form
mass
the quantity of matter that makes up any physical object
law of conservation
matter can neither be destroyed or created but can change form
all matter is made up of building blocks called
atoms
what are the three fundamental components of an atom
neutrons, electrons, protons
what kind of charge does a proton have
positive
what kind of charge does a neutron have
no charge ; neutral
what kind of charge does a electron have
negative
what makes up the nucleus of the atom
neutrons and protons
true or false : do electrons orbit around the atom
true
def energy
the ability to do work
potential energy
stored energy
kinetic energy
energy in motion
wavelength
distance is from crest to crest
amplitude
distance from crest to trough
frequency
the number of crests or troughs that pass a fixed point during a unit of time
what are some characteristics
have no mass, are highly penetrating and invisible, are electrically neutral, are poly energetic and heterogeneous, travel is straight lines at the speed of light, can ionize matter, cannot be focused with a lens, produce biological changes in tissues, produce secondary and scatter radiation
resistance
any property in the circuit that hinders the flow of current ; the ohm is the unit of electrical resistance ; material of conductor, length of conductor, diameter of conductor
current
the quantity of electrons flowing in a circuit ; ampere is the unit used to measure the rate
potential difference
is the force or speed of the electron flow in the current ; volt is the unit used to measure potential difference
parallel circuit
each component has its own direct path to both the negative and positive sides of the circuit
series circuit
the path of electrons from negative to the positive side goes through all the electrical components of the circuit
circuit breaker
any electrical device that will prevent equipment damage if the current gets too high by cutting off the electrical supply to the circuit
preset timers electric timers
impulse precise to the millisecond, used to rapid film production
preset timers electronic timer
used to control add terminate time when the correct mAs has been reached
electromagnetic induction
magnetic fields and electric energy are interrelated ; electricity is produced when a magnet is moved around a conductor or a conductor is moved around a magnet.
AC can be converted so that is flows none direction only, through a process called
rectification
true or false : magnetic fields can produce electricity
true
true or false : electric currents create magnetic fields
true
step up transformer
has more windings on the secondary side ; used to increase the volts to kilovolts
step down transformer
has fewer windings on the secondary side ; used to reduce the voltage
what are the 4 things you need to produce x-rays
vacuum, source of electrons, target, high potential difference
anode
positive end of the tube, the target is located at the anode
cathode
negative end of tube, the filament is part of the cathode
pyrex tube
has has the air removed so that it is nearly perfect vacuum
thermionic emission
as the tungsten filament is heated. electrons in the tungsten atoms orbits spin faster, moving farther away from the nucleus. electrons in outer orbits are flung out of the atoms, forming an electron cloud or space charge ;
this space charge provides the electron source for the x-ray production
quantity
mAs = controls the number of electrons produced = blackening on the film
quality
kilovoltage = force applied to move electrons across tube from cathode to anode
the energy of the electron stream is converted at the anode into heat, how much is converted into heat and into x-rays
99% becomes heat ; 1% becomes x-rays
bremsstrahlung radiation
is created when an incoming electron slows down suddenly near the nucleus of the tungsten atom and abruptly changes direction ; the energy created by slowing down and changing direction results in the creation of an x-ray beam
below 70 kvp what percent is brems interaction
100%
above 70 kV what percent is brems interaction
85%
characteristic radiation
an incoming electron removes an inner orbital electron from the tungsten atom, creating a hole in the k-shell ; when an outer shell electron drops to the fill the hole a characteristics photon is emitted
below 70 kV what percent is characteristics radiation
0%
above 70 kV what percent is characteristic radiation
15%
what are the two types of anodes
stationary, rotating
how fast can a rotating anode spin
standard speed - 3,6000 RPM
high speed - 10,000 RPM
what is the most common target angle
12 degrees
line focus principle
effective focal spot is the vertical projection of the actual or true focal spot
anode heel effect
the intensity of the x-ray beam is least towards the anode end of the field and greater towards the cathode
low kV
high contrast
high kV
low contrast
mA
measures the number of electrons across the tube each second ; the number of electrons in the space charge is controlled by the mA
filtration
placed in the housing of the tube to further reduce the longer, waker wavelength radiation. removes unwanted soft x-rays
what is the required minimum filtration for a machine that runs above 70 kV
2.5 al eq
inherent filtration
glass tube and oil 0.5mm
