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Physics Midterm
LCCC 117
| WTF is This? | No Shit Sherlock |
|---|---|
| Anode Cooling Curve | Shows time needed for ANODE to cool |
| Tube Rating Chart | Shows max technique factors (kVp and T for given mA) |
| HU Formula | HU=kVp x mA x T x FACTOR x # Exposures |
| Single Phase HU Factor | 1 |
| 3-Phase 6-Pulse HU Factor | 1.35 |
| 3-Phase 12-Pulse HU Factor | 1.41 |
| High-Frequency HU Factor | 1.45 |
| What creates "ghost" images/shapes outside the collimated focal spot? | Off Focus (Extrafocal) Radiation |
| What is average ROTOR RPM? What is RPM for high speed Rotor? | 3,000-3,500 RPM Typical 10,000-12,000 RPM Hi Speed |
| Induction motor (________) located outside the Xray tube? | Stator (Electromagnet pairs) |
| Tube Angle Coverage Formula? | C = SID x tanTA x 2 |
| Focal Spot is bigger at Anode end True or False | False - Focal spot smaller at Anode, Bigger at Cathode |
| More photons at Anode end True or False | False - Anode Heel Effect = Less Xrays at Anode end |
| Line Focus Principle | Effective focal spot always smaller than Actual focal spot when angle <45° |
| Why is a sharper Target Angle better? | 1. Greater area to dissipate heat 2. More focused Effective area |
| Actual Focal Spot | Point on anode where Xrays are produced |
| Effective Focal Spot | Functional portion of Xray beam (Central Ray) |
| 3 Reasons Tungsten ideal | 1. High Melting Point 2. High Atomic # 3. Good Heat Conduction |
| Rotating Anode made of? | Tungsten alloy embedded in MOLYBDENUM Disc |
| Stationary Anode made of? Used primarily where? | Tungsten alloy embedded in COPPER Low power DENTAL application |
| What type of Xray tube INCREASES the negative voltage of the focusing cup to control exposure? | Grid-Biased (Grid Controlled) Tube |
| What voltage is used to restrict e- production in Grid-Biased tubes? Where are these used? | -50 Volts Used in Cardiac Cath Labs |
| Max mA output due to Space Charge Effect? | 1,000-1,200 mA |
| Why are Xray tubes limited on mA output? Why not 2,000 mA? | Space Charge Effect |
| Ohm's Law | V=IR Volts=Amps x Resistance |
| Unit of Radioactivity? | Curie or Bequerels |
| Regulated max for Leakage Radiation? | 100 mR/hr at 1 meter |
| What is a series of variable resistors? | mA Selector |
| Selonoid vs Electromagnet | Selonoid just Coil Electromagnet is Coil around FERROMAGNET Core |
| What is the exit point for Xrays from the Glass Envelope? | Window |
| What is the window made of in Molybdenum Tubes? | Beryllium (Mammography tubes) |
| 3 Causes of Tube Failure | 1. Arcing from Tungsten deposits on glass 2. Filament Breakage 3. Bearing Failure |
| Thermionic Emission | Boiling of electrons |
| Minimum Response Time for AEC? | 15-25 ms (Less common 5-6 ms) |
| AEC Backup Timer overrides and terminates exposure at ____ ? | 6 sec or 600 mAs |
| Which AEC used a Fluorescent screen and Photomultiplier Tube to charge a capacitor to terminate exposure? | Phototimer |
| What amperage does the mA selector supply to the tube? | 3-6 amps |
| What converts AC to DC? | Rectifier (Diode, SCR) Usually 1-4+ used |
| In the Xray Tube Circuit, what provides a constant turns ratio to make kVp? | Step Up Transformer (Fixed High Voltage) Ex. 500:1 Gives 40-150 kVp |
| Which type of timer is used with falling load or battery powered portables? | mAs Timer |
| What does a mAs Timer monitor to end exposure? | Time & mA for mAs |
| Electronic Timer uses __________ and is accurate down to _____ ? | Capacitors, 1 ms |
| Which timer is synchronized to the Electrical Waveform? How is time measured? | Synchronous Motor, 1/120 sec = 8 ms |
| What reads incoming Voltage and Displays expected kVp Output? | kVp Meter |
| Primary Voltage of High Voltage Transformer comes from? | Secondary Voltage (Vs) of Autotransformer becomes Primary Voltage (Vp) of High Voltage Transformer |
| What adjusts for changes in voltage supplied to the generator? | Line Compensator |
| 3 Phase 6 Pulse Ripple? 3 Phase 12 Pulse Ripple? | 13%, 3% |
| Converts AC to PULSED DC Current? | Rectification |
| High Frequency Generator Ripple? | <3% |
| Full Wave Rectification (FWR) uses how many diodes? Produces how many pulses? | FWR 4 Rectifiers 120 pulses/sec |
| Half Wave Rectification (HWR) uses how many diodes? Produces how many pulses? | HWR 1 Diode/Rectifier 60 pulses/sec |
| Converts 60 Hz AC to HiFreq pulsed DC... | Hi-Freq Generator - |
| 2 Connection Types for Three Phase Power? | Delta and Wye (Y) |
| Diode that only allows electron flow in ONE Direction | Rectifier |
| Turns Ratio | Ns/Np |
| Voltage is Directly related to Turns Ratio T/F? | True Ns/Np=Vs/Vp |
| Amperage is Directly related to Turns Ration T/F? | False - Inversely Ip/Is=Ns/Np |
| VpIp = VsIs | Current related to Voltage = Power conserved |
| Rotor | Located in Anode Stem tries to align to STATOR's electromagnets |
| Sequential Activation | STATOR's electromagnet pairs fire opposite in circle |
| Anode Rotation Rate? | 3,500-10,000 rpm |
| Generator | Convert Mechanical Energy to Electric Energy |
| Motor | Electricity supplied creates Mechanical Energy |
| Mutual Induction | Varying Electric current flows thru Electromagnet of Primary coil will INDUCE similar current in Secondary coil |
| Faraday's Law | Electric Current induced in Circuit if some part in changing Magnetic Field |
| Total Current in Parallel Circuit | It = I1+I2+I3 |
| Total Voltage in Parallel Circuit | Vt = V1 = V2 = V3 |
| Total Resistance in Parallel Circuit | 1/Rt = 1/R1 + 1/R2 + 1/R3 |
| Rt in Parallel Circuit is always Less than ___ ? | Rt < Any individual R |
| Total Resistance in Series Circuit | Rt = R1 + R2 + R3 |
| Total Current in Series Circuit | It = I1 = I2 = I3 |
| Total Voltage is a Series Circuit | Vt = V1 + V2 + V3 |
| kilowatt formula | kW = (kV x mA)/1,000 |
| Insulator (example) | Does not allow electron flow (Glass) |
| Conductor (example) | Electrons flow easily (Copper) |
| Semiconductor (example) | Electrons flow in ONE Direction (Silicon) |
| Superconductor (example) | Conduct w Less Resistance at LOW temps (Titanium) |
| Electric Current flows from ____ to ____ | Current from + to - |
| Electrons flow from ____ to ____ | Electrons from - to + |
| 3 ways to Electrify an Object | Friction, Contact, Induction |
| Coulumb's Law | F = k (QaQb/d2) F = Force k = Coulumb's constant |
| Charges reside on the OUTER surface of ___ ? | Conductors |
| Charges are dispersed evenly throughout ___ ? | Insulators |
| All charges move along conductors T/F ? | False - Only Negative |
| Photon Energy Formula | E = hf Where f=frequency, h=Plank's constant |
| Wave Equation | V=fλ Where V always speed of light |
| Wavelength (λ) of Xrays | Xrays 0.1-.5 Angstroms |
| Autotransformers operate on what principle? | Self-Induction |
| As Voltage _____ Current _____ | Increases, Decreases |
| What transformer is used in the Filament Circuit? | Step Down |
| Step Down transformer is used to? | Decrease Voltage, Increase Amperage (Current) |
| Step Up transformer does what? | Increase Voltage, Decrease Current |
| Transformers do what? | Increase and Decrease Voltage (or electric potential) through electromagnetic Induction |
| Atomic Number | (Z) # Protons |
| Atomic Mass | (A) # Protons AND Neutrons |
| Force that keeps electons bound to shells? | Centripetal Force |
| Transformer has more turns in primary coil than secondary will | Increase |
| Volt is | Electrical potential |
| Two electrical charges | Either attrack or repel |
| Bohr is | Atomic structure |
| Plank is | Photon energy |
| Colmb is | Electrostatic force |
| Xrays have a longer wavelength then | Gamma |
| When charges exist in conductors | The charge resides on the outside of conductor |
| Both positive and negative move along conductors | False |
| What is the maximum number of electrons in the M shell? | 18 |
| In the coulombs law equation, if the distance is increased how is total force changed? | Decreased |
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RadTechTKD
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