Physics Module 6
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darksydicate on September 28, 2012
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83 terms
Terms | Definitions |
|---|---|
 Autotransformer | operates off the principle of self-induction |
| Alternating current | The type of current in which electrons alternate direction of flow as the electric potential switches back and forth |
| Anode | The positively charged disc at one end of a vacuum tube |
| Automatic Exposure Control (AEC) | A device that controls image density by terminating the exposure at a present density level and automatically adjusts exposures according to patient thickness |
| Autotransformer | A device that raises or lowers voltage in the primary circuit, depending on the setting chosen on the machines control panel for the kVp |
| Capacitor | A device for holding and storing charges of electricity |
| Cathode | The negatively charged element in a vacuum tube or x-ray tube |
| Circuit breaker | If the current flowing through it rises above a certain level, it flips its internal switch to open the circuit and stop electric flow. |
| Current | The stream of electricity that moves along a conductor |
| Current | Volume of flow depends on the difference of potential and the resistance to be overcome. Measured in amperes |
| Direct current | type of current that flows in only one direction |
| Electronic Timer | Timing circuit based on the time required to charge a capacitor through a variable resistor. Most sophisticated, complex and most accurate timer. |
| Exposure Timer | A device that regulates the length of time the electrons are allowed to cross the tube |
| Filaments | A small coil of wire through which current is passed. Used to produce a stream of electrons |
| Filament circuit | The electric circuit that controls filament temperature |
| Focal spot | Target of an x-ray tube which is bombarded by the focused electron stream when the tube is energized |
| Focusing cup | A shell-like device behind and to the sides of the filament that prevents spreading of the electrons as they move from the filament toward the anode |
| Full-wave Rectification | A means of using all of an alternating current that is converted to direct current. changing the negative direction of the AC to the positive direction. |
| High Frequency Generator | Generator providing a nearly constant high voltage waveform for the x-ray tube |
| Insulator | A substance that does not conduct electric current |
| Ionization | The process of turning an atom into an ion by adding or removing an electron |
| Ionization Chamber | A device for measuring ionizing radiation by measurement of the ionization of the gas contained in the chamber |
| kVp Setting | a setting that controls the electric potential difference between the cathode and the anode |
| Line compensator | A device that incorporates a meter to measure the voltage provided to the x-ray imaging system and a control to adjust the voltage to precisely 220V |
| mA meter | A device placed in the tube circuit and used to monitor x-ray tube current |
| mA timer | Monitors the product of mA and exposure time and terminates the exposure when the desired mAs value is attained |
| Mutual Induction | current in one conductor induces a current flow in another conductor |
| N-type crystal | a semiconductor with a few free electrons in its lattice. Made by combining silicon with phosphorus |
| Phototimer | A device used in radiology and photography to control the exposure interval by terminating the exposure when the amount of incident radiation or light reaches a present quantity |
| Primary Circuit | The part of the x-ray equipment circuitry that increases the supplied 220 volts to the level necessary for producing x-rays in conjunction with the secondary circuit |
| P-type crystal | A semiconductor based on a silicon lattice, which has boron atoms mixed in place of some of the silicon atoms |
| Rectifier | a device that converts alternating current to direct current by allowing the current to flow through it in only one direction |
| Resistance | The ability of an element in a circuit to resist the flow of electricity by reducing or impeding it |
| Resistor | an appliance for regulating the resistance and thus controlling the amount of current entering an electric circuit. Rheostat is the most common one. |
| Secondary circuit | The x-ray tube circuit that increases the voltage to the kilovoltage needed to produce x-rays. Rectifies the current from AC to DC |
| Self-induction | The process that occurs in a single coil or wire when an alternating current flows through it and induces a second current to flow in the wire, but in the opposite direction |
| Semi-conducting crystal | Type of material "in between" an insulator and a conductor. some current flow does occur, but with special characteristics |
| Solid-state diode | A rectifier that is made by putting together n-type and p-type semiconductors in a device called a diode |
| Solid-state rectifier | A device used to create a powerful direct current from the supplied alternating current |
| Step-down transformer | A device included in the filament circuit to lower the voltage to the filament |
| Step-up transformer | A device in the primary circuit that raises voltage to the kilovolt level needed to power the x-ray tube |
| Synchronous motor | A precision device designed to drive a shaft at precisely 60 revolutions per second |
| Synchronous timer | A timing mechanism based on a synchronous motor that drives a shaft a precisely 60 revolutions per second |
| Three-phase power | The generation of three simultaneous voltage waveforms out of step with one another, thus never dropping the voltage to zero during exposure |
| Timer Circuit | A circuit made up of a mechanical or electronic device whose action is to start and stop the high voltage across the x-ray tube. Nearly always located in the primary section |
| Transformer | A device that operates on the principle of electromagnetic mutual induction to change the electric potential to higher or lower voltage |
| Transformer law | The principle that there is a direct proportion between the ratio of wire turns and the ratio of voltage |
| Voltage | Unit of measurement for electric potential |
| X-ray tube | Glass vacuum bulb containing two electrodes. Electrons travel at high velocity from cathode to anode, where they are suddenly captured, giving rise to x-rays |
| 500 times | What is the typical increase in voltage from the autotransformer? |
| Autotransformer | Which transformer generally serves as the Kvp selector? |
| Electronic Timer | Which exposure timer incorporates a variable resistor? |
| True | The lower the mA station number, the greater the resistance it represents in the filament circuit. True or False |
| Phototimer | Which Exposure timer has the patient as the variable? |
| Secondary circuit | Where is the x-ray tube located in which circuit? |
| One coil serving as both primary and secondary | What best describes the autotransformer? |
| Because the tube operates best when current flows from anode to cathode | Why are rectifiers necessary in the general x-ray circuit? |
| Solid-state rectifier | A p-n crystal that only conducts electricity in one direction |
| mA station | the lower the mA station number, the higher the resistance |
| Control filament heating | Why are rheostats necessary in x-ray production? |
| Primary and secondary circuit | Which sections of the x-ray circuit provide the kinetic energy needed to produce x-rays? |
| Vs/Vp = Ns/Np | Transformer law |
| With the direction of the arrow of the solid-state rectifier | Which direction does current flow through a solid-state rectifier? |
| Against the direction of the arrow of the solid-state rectifier | Which direction does electrons flow through a solid-state rectifier? |
| 100% | With four rectifiers and one waveform, what is the voltage ripple? |
| Controls duration of filament heating | The exposure timer does what in the general x-ray circuit? |
| Synchronous timer | Which exposure timer is based on how fast a motor turns a shaft? |
| Rectifier | Which component serves to send electricity through the x-ray tube in the same direction each time? |
| Step-up transformer | Which component increases voltage about 500 times? |
| Step-down transformer | With which transformer type would a radiographer be more interested in the output current? |
| High Frequency | Which waveform has the least voltage ripple? |
| 4 | How many rectifiers are necessary to create a single-phase full wave waveform? |
| Photodiode Sensing Device | uses a photomultiplier tube that converts radiation to light to electric charges |
| Spinning top | Heavy metal disc 5-25 cm in diameter rests on low friction pedestal so that it can be rotated 1 rps. Used for single phase |
| Synchronous spinning top | uses a synchronous motor turning 1 rps. Used to test three-phrase systems |
| Rectification | process of changing AC to DC |
| Half-wave rectification | Suppressing the negative half of the AC cycle |
| Valve-tube rectifiers | Used up to the 1950's so they are in the older machines |
| Monoenergenic | Every energy is different wavelengths |
| Polienergenic | Same wavelength energy |
| 3 Phase 6-pulse | Has 13% ripple |
| 3 Phase 12-pulse | Has 4% ripple |
| Single Phase Power | Has 100% ripple |
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