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Physics Unit 3 Exam
| Question | Answer |
|---|---|
| part of the x-ray circuit that contains the kvp selector, kvp meter, exposure timer and exposure switch | primary side/circuit |
| part of the x-ray circut that contains the mA selector, focal spot selector and step-down transformer | filament circuit |
| part of the x-ray circuit that contains the mA meter and rectifiers | secondary side/circuit |
| adjusts autotransformer to deliver precisely 220 volts | line voltage compensator |
| supplies a precise voltage to the high voltage circuit | autotransformer |
| reads the voltage that will be applied to the secondary side of the step up transformer | kVp meter |
| filament uses this current | 3 to 6 A |
| this is what happens to current when voltage is increased | decreased |
| this is what happens to voltage when current is increased | decreased |
| type of timer that has a minimum exposure time of 1/60 s and has to be reset each time exposure is made | synchronous |
| type of timer that is the most accurate but also most sophisticated and complicated | electronic |
| type of timer that monitors the product of mA and exposure time and terminates the exposure when desired mAs value is attained; used on falling load imaging systems | mAs |
| type of timer that measures the quantity of radiation reaching the image receptor and terminates the exposure when the image receptor has received enough radiation to provide the required optical density | AEC |
| most commonly used AEC | ionization chamber |
| type of rectifiers used in x-ray imaging systems today | solid-state |
| if positive charge is applied to the n side of the solid state rectifier then electrons____ flow | will not |
| if negative charge is applied to the n side of the solid state rectifier then electrons _____ flow | will |
| number of rectifiers used in half-wave rectification | two |
| number of rectifiers used in full-wave rectification | four |
| number of pulses per second with half wave rectification | 60 |
| number of pulses per second with full wave rectification | 120 |
| number of pulses per second with three phase power (non rectified/6 pulse) | 360 |
| number of pulses per second with three phase power (rectified/12 pulse) | 720 |
| type of generator that generates high voltage, full-wave rectified power to a higher frequency (usually 500-25,000 Hz) | high-frequency |
| type of generator used in portable machines | high-frequency |
| type of generator that builds up a charge then releases it with completion of the circuit | capacitor-discharge |
| type of generator that is used to provide the highest mA setting at the shortest possible times where the computer will automatically calibrate the time of the exposure allowing consistently shorter exposures | falling-load generator |
| voltage ripple percent for single phase half wave rectified units | one hundred |
| voltage ripple percent for single phase full wave rectified units | one hundred |
| voltage ripple percent for three phase, six pulse units | thirteen |
| voltage ripple percent for three phase, twelve pulse units | four |
| voltage ripple percent for three phase, high frequency units | less than 1 |
| X-ray production efficiency ______ with an increase in voltage ripple | decreases |
| High frequency generators cost _____ than single phase generators | more |
| multiplying mA and kVp then dividing by 1000 is the equation for power rating for _______. | three phase and high frequency |
| multiplying 0.7, mA, and kVp then dividing by 1000 is the equation for power rating for _____. | single phase units |
| What is a diode? | devices that allow current to flow in only one direction |
| What is Thermionic Emission? | |
| What is space charge? Space Charge Effect? | |
| What is saturation current? | |
| What is extrafocal/off focus radiation? | |
| What does AEC measure? | the amount of radiation that makes it through the patient and to the detector |
| What is an electronic exposure timer? | the precision timing system in X-ray machines, using capacitor–resistor circuitry to deliver exact, repeatable exposure durations |
| What is a synchronous exposure timer? | controls the duration of an X-ray exposure at a constant speed |
| In a high frequency full wave, ____ of power is converted to 500-25,000 Hz THEN transformed to higher voltage | 60 Hz |
| Which voltage ripple is the most efficient/most costly? | <1% |
| power rating is measured in | kiloWatts |
| What is the most common cause of tube failures? | abrupt failure in electron arcing |
| What 3 materials are the anode made of? | Tungsten, Molybdenum, and Graphite |
| rotating vs stationary anode | Stationary anodes are simpler and more reliable, while rotating anodes offer better heat dissipation and higher power output |
| which material has a high atomic number and high heat? | tungsten |
| where are x-rays emitted? | focal spot |
| What is the effective focal spot? | the area projected onto the patient and image receptor |
| What is the actual focal spot? | where electrons interact with target |
| The smaller the anode angle, the larger is the ______ _____ | heel effect |
| Electron Cloud? | space charge (when the electrons are in vicinity of the filament before acceleration to anode) |
| Space Charge Effect? | the cloud of electrons makes it hard for subsequent electrons to be emitted because of electrostatic repulsion |
| the anode is a thermal _______ | dissipator |
| What are the three main components of the xray imaging system? | the tube, the operating console, and the high voltage generator |
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