Ch 4: The Xray Circuit Flashcards
define electrodynamics
electricity
electric charges in motion
What is a circuit?
a series of moving charges with occasional object or device that affects the flow
T/F A closed circuit is a complete path where the electricity will flow.
True
What is an open circuit?
pathway of electron/electrical flow is broken
happens when you turn off a light switch (opens the circuit)
Describe the electron flow in a Direct current
electrons flow in 1 direction
positive and negative end
Why is a DC important in the xray tube
so electrons flow one direction from cathode to anode
describe an alternating current
electrons flow rapidly back and forth, changing direction
created by specialized generators
this generator changed the charge (polarity) making electrons flow in different directions
Electricity usually results from the movement of the….
electrons through the circuit
Electric potential is measure in….
volts
Electric potential is selected on the generator as…
kvp
Electric current is measured in…
amperes
electric current is selected on the generator as…
mA
electric resistance is measured in…
Ohm’s
Equation for Ohm’s Law
V = IR
v - voltage
I - current
R - resistence
What are two types of Electric current?
Alternating current
direct current
How are the two types of electric current different?
Alternating: electron flows in both directions, fluctuating voltage
Direct: electrons flow in one direction, stable voltage
Differentiate between conductor and insulator
conductor - supports the travel of electricity
insulator - resist electrical flow
Define electromagnetism
any flow of electrons are surrounded by magnetic field
Define self-induction
fluctuating magnetic field cuts through the turns of the coil creating opposing voltage
(primary/secondary)
Define mutual induction
electricity induced in a secondary coil by a moving magnetic field
(step up/step down transformers)
What is a transformer?
devices that convert electrical current from one potential diff (voltage) to another
Why are transformers important in xray?
they are able to increase/decrease the voltage from the electricity in the wall to the voltage needed for creating the xray being done
Define autotransformer
serves as both primary and secondary coil
single core and wire coil around it
turns ratio depends on technique selection
What kind of transformer(s) use mutual induction?
step up and step down transformers
What kind of transformer(s) use self-induction?
autotransformer
Define step-up transformer
more coils in the secondary side of the transformer
increases voltage
Define step-down transformer
more coils in the primary side of the transformer
decreases voltage
Differentiate between the three types of transformers used in xray circuit
Auto - self-induction, can act as a step up or step down transformer, ability to increase or decrease voltage
Step Up - more coils on the secondary side, increases voltage
Step Down - more coils on the primary side, decreases voltage
What are the three sections of the xray circuit?
primary (low voltage) side
secondary (high voltage) side
filament circuit
What are the three main components of the x-ray circuit and what is involved in each?
High voltage power supply - transformers
control unit to manipulate the power - generator
X-ray tube - creating the x-rays
Define rectification
converting AC to DC
xray circuit is a full wave rectification circuit using 4 rectifiers
Within an electrical circuit, the term “current” refers to the movement of what?
electrons
In an electrical circuit, the term “voltage” refers to what?
electrical force that moves the electrons through the circuit
Commercial power supplying the xray circuit is _____ (direct, alternating) current
alternating
What is the primary difference between an AC and DC within an electrical circuit?
direction of electron flow
What component of the xray circuit needs to use alternating current in order to function?
transformers
Why must an xray tube be supplied direct current?
The electrons need to flow in one direction to prevent damage to the tube - cannot have electrons flowing back into the cathode
Electrons move from cathode to anode ONLY
T/F Direct current changes polarity but keeps a constant, stable voltage.
False
DC does not change polarity (direction/charge)
The difference in electrical charge between two points in a circuit is called the…
voltage
What is the function of the rectifier within the xray circuit?
convert AC to DC
The rectifier is located where in the xray circuit?
step-up transformer and the xray tube
T/F Alternating current alternates between negative and positive polarity
True
change in polarity causes the electrons to rapidly change directions
What is half-wave rectification?
the negative portion of the pulse is removed, leaving large gaps between positive voltage peaks where xrays cannot be made
what type of rectifier is used in modern day xray equipment?
Diode-based rectification
What is a diode?
small electric device that allows alternating current to come in, but only direct current to go out
What type of rectification occurs when negative voltage peaks are turned into positive voltage peaks
full-wave rectification
a transformer operates on what principle?
electromagnetic induction
How do step-up transformers affect amperage and voltage?
increase voltage, decrease amperage
which type of transformer is incorporated within the high voltage portion of the xray circuit
step up transformer
Define electromagnetic induction
magnetic field creates an electric current to flow
How do you determine the turns ratio of a transformer?
ratio: number of secondary coils to number of primary coils
A step down transformer has ___ (more/less) coils in the primary side than the secondary side
more
If there are more coils in the secondary side of the transformer, what kind of transformer is it?
step up transformer
What type of transformer is needed for the filament in the xray circuit in order for thermionic emission to be possible? Why?
step down transformer
increases amperage to the level needed to heat up for thermionic emission
