The Xray Circuit
Electrons are converted into X-ray photons in the: 1.Filament circuit 2.Secondary circuit 3.Primary Circuit 4.X-ray tube A. 2 & 4 B. 1 & 2 C. 1 only D. 4 only
A. 2 & 4 The X-ray tube, which is located in the secondary circuit, is where electrons are converted into X-ray photons. This is done when potential difference (kVp) is applied to the tube and current flows from cathode to anode. Electrons produced from the tungsten filament, which is located at the cathode, are accelerated towards the anode. This interaction, between electrons and the anode target, is what leads to the production of X-ray photons.
The removal of the bottom, negative oscillating wave is known as? A. Half-wave rectification B. Full-wave rectification C. Single-wave rectification D. Bottom-wave rectification
A. Half-wave rectification Feedback: The term, "half-wave rectification" describes the removal of the negative oscillating wave that is present in alternating current (AC).
The kVp meter on the primary side of the X-ray circuit: A. Measures low voltage and reads in kilo-voltage B. Measures kilo-voltage and reads in low voltage C. Measures kilo-voltage delivered by the step-up transformer D. Measures kilo-voltage delivered by the auto transformer
A. Measures low voltage and reads in kilo-voltage It is low voltage that is produced on the primary side of the X-ray circuit. This low voltage, produced by the autotransformer, is read by the kVp meter and translated into kilo-voltage.
In a step-down transformer, which coil has the most wire turns? A. Primary coil B. Secondary coil C. Both have the same number of turns
A. Primary coil Remember, the amount of turns in the secondary coil is what determines if a transformer will step-up or step-down the voltage. The greater amount of turns in the secondary coil of a step-up transformer will result in greater voltage, and fewer turns in the secondary coil of a step-down transformer will result in lesser voltage.
Single-phase generators are inefficient since they produce waves that fall to zero before returning to 100%. A. True B. False
A. True Feedback: This is true. The falling between zero and 100% causes there to be a short gap between X-ray photon production. This short gap means that a larger mAs must be used in order to produce a diagnostic X-ray beam.
Tube current is measured in: A. mA B. A C. Voltage D. Kilo-voltage
A. mA The current that flows from cathode to anode inside the X-ray tube is measured in mA, and the current that flows to the filament is measured in A. Remember, as voltage goes up, the current goes down. The massive increase of voltage that occurs on the secondary side of the step-up transformer leads to the current that travels across the tube to be dropped to the levels of mA.
Find the new voltage using the Transformer law formula: Secondary voltage = 100 Primary voltage = x Secondary turns = 50 Primary turns = 200 A. 450 volts B. 400 Volts C. 250 volts D. 150 volts
B. 400 Volts Feedback: Secondary voltage (100) x Primary turns (200) = 20,000 Secondary turns (50) x Primary voltage (x) = 50x 50x = 20,000 50 50 x= 400
The auto transformer changes voltage using: A. Two coils of wire, each wrapped around an iron core B. A single core of wire wrapped around an iron core C. The kVp meter to select desired voltage D. The kVp meter to select desired kilo-voltage
B. A single core of wire wrapped around an iron core The autotransformer is a single coil of wire with an iron core that has a number of connections along its length. Depending on which connections are chosen, the autotransformer will step-up or step-down the voltage sent to the step-up transformer.
The rectification system converts: A. DC into AC B. AC into DC C. AC/DC into kilovolts D. Kilovolts into AC/DC
B. AC into DC The tube current, or current flowing from cathode to anode, must only do just that. If current was to alternate between the cathode and anode, the results would be harmful to the tube and would impede the production of X-ray photons. The rectification system is comprised of diodes that only allow the flow of current in one direction. These diodes converts the AC that is coming from the step-up transformer into the DC that is sent to the X-ray tube.
The rectification system is responsible for: A. Increasing current before it reaches the X-ray tube B. Allowing current to only flow in one direction C. Decreasing current before it reaches the X-ray tube D. Allowing current to flow in more than one direction
B. Allowing current to only flow in one direction The rectification system is responsible for converting AC into DC. It uses electronic diodes that only allow the current to flow in one direction. Using a combination of four of these diodes allows for the complete rectification of both, the positive and negative, wave forms of AC before it reaches the X-ray tube. Transformers are responsible for the level adjustments of voltage and current.
The rectification system is located: A. On the primary side of the X-ray circuit B. Between the secondary side of the step-up transformer and the X-ray tube C. Between the autotransformer and the step-up transformer D. Between the primary side of the step up transformer and the X-ray tube
B. Between the secondary side of the step-up transformer and the X-ray tube Remember, before the current coming from the secondary side of the step-up transformer can be delivered to the X-ray tube, it needs to be rectified. The rectification system converts AC into DC using diodes that only allow the flow of current in one direction.
When potential difference (kVp) is applied across the X-ray tube, electrons flow from: A. The mA meter to the kVp meter B. Cathode to anode C. The kVp meter to the mA meter D. Anode to cathode
B. Cathode to anode In order to prevent tube damage and for the X-ray tube to function properly, the current that flows inside the X-ray tube must only flow from cathode to anode. The rectification system in the X-ray circuit is what makes this possible. It converts the AC that is delivered by the step-up transformer into DC before the current is delivered to the tube.
With all factors remaining constant, a generator with 100% percent voltage ripple will have this effect on receptor exposure. A. Increase receptor exposure B. Decrease receptor exposure C. No effect on receptor exposure
B. Decrease receptor exposure Feedback: Generator with 100% voltage ripple are the least efficient at producing X-ray photons due to the wave form having to oscillate between 100% and 0%.
Select the term that describes the main component used within a rectifier(s): A. Rheostat B. Diode C. Transformer D. Generator
B. Diode Feedback: Diodes are the main component within rectifiers. Diodes work by allowing current to flow in only one direction.
This type of current must be delivered to the X-Ray tube for the production of photons to occur. A. Alternating Current (AC) B. Direct Current (DC)
B. Direct Current (DC) Feedback: Direct current is the only type of electricity that can be used in the production of X-ray photons. The use of alternating current would cause the X-ray tube current to flow in the wrong direction (anode to cathode not cathode to anode).
A Transformers can only function through the supply of DC current. A. True B. False
B. False Feedback: This is false, A transformer must have alternating current (AC) in order for mutual induction to occur.
Diodes are able to be placed within a rectifier in either direction based on the incoming current. A. True B. False
B. False Feedback: This is false. A diode can only be placed in one direction since diodes allows current to pass in only one direction.
The step-down transformer is located in the: A. Primary circuit B. Filament circuit C. Secondary circuit D. X-ray tube
B. Filament circuit The step-down transformer is located in the filament circuit. In order to increase the current necessary for the desired level of thermionic emission in the filament, there needs to be a decrease the voltage. This is done with a step-down transformer. Remember, when there is a decrease in voltage, there is an increase of current.
Filament temperature is controlled by the: A. mA meter B. Filament current C. The step-up transformer D. Tube current
B. Filament current Filament current is what determines the temperature of the tungsten filament. The more current that is delivered from the step-down transformer, the higher the temperature of the tungsten filament. The higher the temperature of the filament, the more electrons are burned off and are available for the production of X-rays once potential difference (kVp) has been applied to the tube.
Mutual induction in the X-ray circuit is used to produce: A. Low voltage for the primary side of the circuit B. High voltage for the secondary side of the circuit C. Low voltage for the secondary side of the circuit D. High voltage for the primary side of the circuit
B. High voltage for the secondary side of the circuit In order to produce the voltage necessary to make a radiographic exposure, we need to convert the low voltage supplied by the autotransformer into levels of kilo-voltage. This is done by using a step-up transformer located on the secondary side of the X-ray circuit. This process is referred to as mutual induction.
Decreasing voltage ripple has what effect on image quality? A. Decreases B. Increases C. Does not affect image quality
B. Increases Feedback: Decreasing the voltage ripple increases image quality since low voltage ripples produce a more consistent X-ray beam.
What is the relationship between filament current and voltage coming from the secondary side of the step-down transformer? A. Functional relationship B. Indirect relationship C. Co-dependent relationship D. Direct relationship
B. Indirect relationship Remember that due to the law of conservation, when voltage drops current increases, and when voltage increases current drops. The product of voltage and current will always equal total power. This means that the relationship between voltage and current is indirect.
A greater amount of wire windings on the primary side of the transformer will produce: A. Greater voltage B. Less voltage
B. Less voltage Feedback: Voltage is reduced when there are fewer wire windings on the secondary side of the transformer compared to the primary side.
In order for a transformer to increase voltage, it must have: A. Greater wire windings on the primary side B. Less wire windings on the primary side
B. Less wire windings on the primary side Feedback: A "step-up" transformer will have a greater amount of wire windings on the secondary side compared to that of the primary side.
The exposure timer is: A. Connected to the autotransformer B. Located on the primary side of the X-ray circuit C. Located on the secondary side of the filament circuit D. Located on the secondary side of the X-ray circuit
B. Located on the primary side of the X-ray circuit The primary side of the X-ray circuit controls the delivery of voltage to the step-up transformer and that is why the exposure timer is located on the primary side. It's an electronic device whose job is to "make" or "break" the voltage that travels across the X-ray tube.
Voltage supplied from the autotransformer is considered: A. High voltage produced through mutual induction B. Low voltage produced through self induction C. High voltage produced through mutual induction D. Low voltage produced through self induction
B. Low voltage produced through self induction The autotransformer supplies the X-ray circuit with what is considered low voltage. It is both, safer and easier, to control and change voltage at lower levels than higher levels. This is done with a single coil using a process called self induction. Voltage is then increased to the level of kilo-voltage when it crosses from the primary side of the circuit to the secondary side using a step-up transformer and a process called mutual induction.
What type of transformer would have a turn ratio of 0.5:1? A. Step-up B. Step-down
B. Step-down Feedback: Since the turn ratio is not a whole number, you can infer that the primary side has more wire turns than the secondary side. 10 turns secondary side divided by 20 turns primary side = 0.5:1 ratio.
What voltage ripple is associated with full-wave rectification? A. 4% B. 14% C. 100% D. 50%
C. 100% Feedback: With full-wave rectification, the wave must fall to the zero line before reaching 100%. This 100% decrease in current causes the circuit to produce an 100% voltage ripple.
What voltage ripple is associated with a three phase, twelve pulse generator? A. 100% B. 14% C. 4% D. 25%
C. 4% Feedback: A three phase, twelve pulse generator produces a 4% voltage ripple since the oscillating wave only falls 4% below 100% total energy.
A transformer with 100 wire windings on the primary side and 500 wire winding on the secondary side would have a ratio of: A. 500:100 B. 2:1 C. 5:1
C. 5:1 Feedback: The transformer ratio is found by dividing the wire turns of the secondary side by the wire turns of the primary side. In this example, there would be 5 turns on the secondary side to every 1 turn on the primary side.
The reason an X-ray circuit requires AC is: A. Because the X-ray tube requires AC in order to function B. Because the rectification system will not work with DC C. Because mutual induction is not possible without AC D. Because the rectification system will not work with AC
C. Because mutual induction is not possible without AC Both, the filament circuit and the secondary circuit, are supplied by voltage that is adjusted through the use of transformers. These types of transformers require AC in order to function properly. The filament circuit uses a step-down transformer, and the secondary circuit uses a step-up transformer. Both of these work through a process known as mutual induction.
In the event the X-ray machine attempts to draw too much power, damage to the entire circuit is prevented by the: A. Auto transformer B. Rectifier circuit C. Circuit breaker D. Line compensator
C. Circuit breaker The circuit breaker, located on the primary side of the X-ray circuit, will stop incoming voltage by "breaking" the circuit. This protects the entire circuit from being damaged in the event the X-ray machine attempts to draw too much power.
The rectifier's role within the X-ray circuit is to: A. Convert low voltage to high voltage B. Convert high voltage to low voltage C. Convert AC to DC D. Convert DC to AC
C. Convert AC to DC The role of rectification within the X-ray circuit is to convert alternating current (AC) to direct current (DC).
The large, solid part of the transformer is best known as the: A. Primary side B. Secondary side C. Core D. Resistor
C. Core Feedback: The largest portion of the transformer is the core. The core is typically composed of iron and is where the tightly wound wire located.
The step-up transformer changes voltage through a process called: A. Self induction B. Rectification C. Mutual induction D. Line compensation
C. Mutual induction Mutual induction uses two coils of wire placed next to each other: A primary coil and a secondary coil. If the secondary coil has more windings than the primary coil, this is called a step-up transformer because it increases voltage. If the secondary coil has fewer windings than the primary coil, this is called a step-down transformer because it decreases voltage.
The X-ray circuit is comprised of which three circuits? A. Primary circuit, high voltage circuit, and the filament circuit B. Primary circuit, secondary circuit, and the step-up circuit C. Primary circuit, secondary circuit, and the filament circuit D. Primary circuit, low voltage circuit, and the high voltage circuit
C. Primary circuit, secondary circuit, and the filament circuit The X-ray circuit is comprised of three separate circuits: the primary circuit, the secondary circuit and the filament circuit.
The technologist chooses the desired kVp setting using the autotransformer through a process called: A. Mutual induction B. Rectification C. Self induction D. Voltage ripple
C. Self induction kVp is selected using an autotransformer, a single coil of wire wrapped around an iron core. Connections are made along different points on the wire in order to increase or decrease voltage to desired levels. This process is referred to as self induction because there is only one coil.
Voltage to the filament circuit is provided by: A. The step-up transformer B. The step-down transformer C. The autotransformer D. mA meter
C. The autotransformer Voltage to the filament circuit is sent from the autotransformer to the rheostat and then delivered to the step-down transformer. The step-down transformer is what lowers voltage and increases the current delivered to the tungsten filament at the cathode.
The process of creating electrons through heating a tungsten filament is referred to as: A. Potential difference B. mA C. Thermionic emission D. Rectification
C. Thermionic emission Thermionic emission is the process of burning off electrons from the tungsten filament located at the cathode. The level of mA is determined by the number of electrons burned off, but does not refer to the process of thermionic emission.
The role of the transformer is to increase or decrease: A. Current B. Resistance C. Voltage D. Watts
C. Voltage Feedback: The transformers role within the X-ray circuit is to either increase or decrease voltage.
The secondary side of the step-up transformer is located in the secondary X-ray circuit and is responsible for: 1.Converting low voltage into kilo-voltage 2.Converting voltage using the process of self induction 3.Converting kilo-voltage into low voltage 4.Converting voltage using the process of mutual induction A. 1 only B. 2 & 4 C. 1 & 3 D. 1 & 4
D. 1 & 4 In order to make an X-ray exposure, the X-ray tube requires voltage in the levels of kilo-volts. This is achieved by converting the low voltage that is delivered by the autotransformer into high voltage using a step-up transformer. The step-up transformer uses a process called mutual induction to convert low voltage into high voltage.
Decreasing voltage to the filament circuit will result in: 1.Decreased thermionic emission 2. Increased electron production at the cathode 3.Increased thermionic emission 4.Decreased electron production at the cathode A. 1 only B. 2 only C. 3 & 4 D. 2 & 3
D. 2 & 3 When there is a decrease voltage in the filament circuit, there is an increase in current. Higher levels of current will result in a tungsten filament that reaches a higher temperature. This will cause more electrons to be burned off through thermionic emission. Both, b and c are correct.
Which of the following are necessary for the process of mutual induction? A. DC B. Rectifiers C. AC/DC D. AC E. Electronic diodes
D. AC Transformer, which use the process of mutual induction, will only operate with a changing electric current (AC). If the primary side of an electric transformer receives DC, it will induce no current in the secondary side. The electronic diodes that make up the rectification system are what converts the AC coming from the secondary side of the step-up transformer into DC before it reaches the X-ray tube.
The step-down transformer is responsible for: A. Raising voltage and raising current B. Lowering voltage and lowering current C. Raising voltage and lowering current D. Lowering voltage and raising current
D. Lowering voltage and raising current The step-down transformer that is located in the filament circuit is responsible for lowering voltage and increasing the current that is delivered to the tungsten filament.
The rheostat is a variable resistor and is located: A. On the secondary side of the step-down transformer B. On the primary side of the step-up transformer C. On the secondary side of the step-up transformer D. On the primary side of the step-down transformer
D. On the primary side of the step-down transformer The rheostat is a variable resistor that is highly precise. It is used to adjust levels of voltage coming from the autotransformer, once the technologist has made an mA selection. The rheostat controls the amount of voltage that is sent to the primary side of the step-down transformer.
The secondary circuit contains: A. The autotransformer, the step-up transformer, and the X-ray tube B. The primary side of the step-up transformer, the kVp meter, and the X-ray tube C. The rectification system, the step-down transformer, and the X-ray tube D. The secondary side of the step-up transformer, the rectification system, and the X-ray tube E. The autotransformer, the step-down transformer, and the X-ray tube
D. The secondary side of the step-up transformer, the rectification system, and the X-ray tube The X-ray circuit is three separate circuits combined: the primary circuit, the secondary circuit, and the filament circuit. The secondary circuit contains the secondary side of the step-up transformer, the rectification system, and the X-ray tube.
Formula for the transformer law of voltage
V₂ / V₁ = N₂ / N₁ V= voltage, N = number of turns, ₁ = primary coil, ₂ = secondary coil.