X-RAY MACHINE CIRCUITS & GENERATORS
Chapter 8 — Answers with Rationales
Basic Circuits
1. What are the three sections of the main x-ray circuit?
Answer: Console, high-voltage circuit, x-ray tube circuit
Rationale: The console controls technique, the high-voltage circuit produces kVp, and the tube
circuit generates x-rays.
2. What protects the entire x-ray circuit from overloads?
Answer: Circuit breaker
Rationale: A breaker automatically opens the circuit during overloads or shorts to prevent
damage. X-RAY MACHINE CIRCUITS & GENERATORS Chapter 8 — Answers with
Rationales
3. Device that compensates for incoming voltage variations?
Answer: Line voltage compensator
Rationale: It corrects fluctuations before voltage reaches the autotransformer.
4. Which console controls set the autotransformer?
Answer: kVp (major and minor)
Rationale: kVp selection adjusts voltage via the autotransformer.
5. Typical turns ratio of the step-up transformer?
Answer: 500:1 to 1,000:1
Rationale: A large ratio is required to raise voltage to diagnostic levels.
6. What differs between AC waves before and after step-up transformation?
Answer: Amplitude
Rationale: Frequency remains constant; voltage change is shown by wave height.
Rectification & Diodes
7. Minimum number of rectifiers for full efficiency (single-phase)?
Answer: 4
Rationale: Four diodes are required for full-wave rectification.
8. Solid-state diode construction?
Answer: N-type and P-type silicon
Rationale: Joining these creates a semiconductor junction.
,9. What bridge allows current to flow at the junction?
Answer: Potential bridge
Rationale: Electron-hole interaction allows conduction.
10. What happens when AC reverses direction?
Answer: The diode becomes polarized
Rationale: Polarization blocks current in the reverse direction.
11. Final step before high voltage enters the tube?
Answer: Rectification
Rationale: X-ray tubes require DC, not AC.
Filament Circuit
12. Process that releases electrons from the filament?
Answer: Thermionic emission
Rationale: Heat causes electrons to boil off the filament.
13. What is required to heat the filament?
Answer: High amperage
Rationale: Heat is produced by current, not voltage.
14. Filament current flows when which button is pressed?
Answer: Rotor
Rationale: The rotor initiates filament heating and anode rotation.
15. Why is there a delay after pressing rotor?
Answer: To heat the filament
Rationale: Electrons must be released before exposure.
16. Excessive rotoring causes what?
Answer: Wear and tear
Rationale: Prolonged heating shortens filament life.
17. Turns ratio of filament step-down transformer?
Answer: 1:44
Rationale: Low voltage and high current are required.
18. Why isn’t filament current rectified?
Answer: It doesn’t cross the tube
Rationale: Rectification is only needed for tube current.
Meters & Measurements
,19. mA station selection routes current through what?
Answer: Resistor
Rationale: Different resistors control filament current levels.
20. Meter in series measures what?
Answer: Amperage
Rationale: Current must pass through the meter.
21. Why is a voltmeter placed in parallel?
Answer: It compares voltage between two points
Rationale: Voltage is potential difference.
22. What voltmeter prevents shock at the console?
Answer: Pre-reading voltmeter
Rationale: It avoids placing high voltage at the console.
23. Console mA meter measures current flowing where?
Answer: Across the x-ray tube
Rationale: Tube current determines x-ray quantity.
24. Tube current is what portion of filament current?
Answer: A fraction
Rationale: Only some electrons cross the tube.
25. mA meter placement?
Answer: Between the step-up transformer and the x-ray tube
Rationale: This ensures tube current measurement.
Generator Types
27. X-ray unit with no rectifiers?
Answer: Self-rectified
Rationale: The tube itself blocks reverse current.
28. Half-wave rectifiers do what?
Answer: Block reverse current
Rationale: Only positive pulses reach the tube.
29. Why must techniques be doubled?
Answer: Only 60 pulses/sec are produced
Rationale: Half the available x-ray output is lost.
30. Average kVp in single-phase systems?
Answer: One-third of peak kVp
Rationale: Voltage drops to zero between pulses.
, 31. In three-phase systems voltage never drops to?
Answer: Zero
Rationale: Overlapping pulses maintain voltage.
32. Voltage fluctuation is called?
Answer: Ripple
Rationale: Ripple describes variation in kVp.
33. Average voltage in three-phase systems?
Answer: 91%
Rationale: Less ripple increases effective voltage.
34. Increased effective voltage improves what?
Answer: Penetration
Rationale: Higher average energy produces more penetrating beams.
35. Effective mA in three-phase systems is?
Answer: Increased
Rationale: Overlapping pulses increase electron flow.
36. Practical mAs adjustment for three-phase units?
Answer: Reduce by half
Rationale: Increased efficiency requires less exposure.
37. Ripple in a 12-pulse generator?
Answer: 4%
Rationale: Multiple pulses smooth voltage output.
High-Frequency & Power
38. High-frequency generator range?
Answer: 500–25,000 Hz
Rationale: Higher frequency produces near-constant voltage.
39. Why use lower kVp on HF mobiles?
Answer: Average kV ≈ set kVp
Rationale: Minimal ripple increases beam energy.
40. High-mA generators allow what?
Answer: Very short exposure times
Rationale: High mA reduces motion blur.
41. Generator power rating units?
Answer: Kilowatts (kW)
Rationale: Indicates output capacity.
Chapter 8 — Answers with Rationales
Basic Circuits
1. What are the three sections of the main x-ray circuit?
Answer: Console, high-voltage circuit, x-ray tube circuit
Rationale: The console controls technique, the high-voltage circuit produces kVp, and the tube
circuit generates x-rays.
2. What protects the entire x-ray circuit from overloads?
Answer: Circuit breaker
Rationale: A breaker automatically opens the circuit during overloads or shorts to prevent
damage. X-RAY MACHINE CIRCUITS & GENERATORS Chapter 8 — Answers with
Rationales
3. Device that compensates for incoming voltage variations?
Answer: Line voltage compensator
Rationale: It corrects fluctuations before voltage reaches the autotransformer.
4. Which console controls set the autotransformer?
Answer: kVp (major and minor)
Rationale: kVp selection adjusts voltage via the autotransformer.
5. Typical turns ratio of the step-up transformer?
Answer: 500:1 to 1,000:1
Rationale: A large ratio is required to raise voltage to diagnostic levels.
6. What differs between AC waves before and after step-up transformation?
Answer: Amplitude
Rationale: Frequency remains constant; voltage change is shown by wave height.
Rectification & Diodes
7. Minimum number of rectifiers for full efficiency (single-phase)?
Answer: 4
Rationale: Four diodes are required for full-wave rectification.
8. Solid-state diode construction?
Answer: N-type and P-type silicon
Rationale: Joining these creates a semiconductor junction.
,9. What bridge allows current to flow at the junction?
Answer: Potential bridge
Rationale: Electron-hole interaction allows conduction.
10. What happens when AC reverses direction?
Answer: The diode becomes polarized
Rationale: Polarization blocks current in the reverse direction.
11. Final step before high voltage enters the tube?
Answer: Rectification
Rationale: X-ray tubes require DC, not AC.
Filament Circuit
12. Process that releases electrons from the filament?
Answer: Thermionic emission
Rationale: Heat causes electrons to boil off the filament.
13. What is required to heat the filament?
Answer: High amperage
Rationale: Heat is produced by current, not voltage.
14. Filament current flows when which button is pressed?
Answer: Rotor
Rationale: The rotor initiates filament heating and anode rotation.
15. Why is there a delay after pressing rotor?
Answer: To heat the filament
Rationale: Electrons must be released before exposure.
16. Excessive rotoring causes what?
Answer: Wear and tear
Rationale: Prolonged heating shortens filament life.
17. Turns ratio of filament step-down transformer?
Answer: 1:44
Rationale: Low voltage and high current are required.
18. Why isn’t filament current rectified?
Answer: It doesn’t cross the tube
Rationale: Rectification is only needed for tube current.
Meters & Measurements
,19. mA station selection routes current through what?
Answer: Resistor
Rationale: Different resistors control filament current levels.
20. Meter in series measures what?
Answer: Amperage
Rationale: Current must pass through the meter.
21. Why is a voltmeter placed in parallel?
Answer: It compares voltage between two points
Rationale: Voltage is potential difference.
22. What voltmeter prevents shock at the console?
Answer: Pre-reading voltmeter
Rationale: It avoids placing high voltage at the console.
23. Console mA meter measures current flowing where?
Answer: Across the x-ray tube
Rationale: Tube current determines x-ray quantity.
24. Tube current is what portion of filament current?
Answer: A fraction
Rationale: Only some electrons cross the tube.
25. mA meter placement?
Answer: Between the step-up transformer and the x-ray tube
Rationale: This ensures tube current measurement.
Generator Types
27. X-ray unit with no rectifiers?
Answer: Self-rectified
Rationale: The tube itself blocks reverse current.
28. Half-wave rectifiers do what?
Answer: Block reverse current
Rationale: Only positive pulses reach the tube.
29. Why must techniques be doubled?
Answer: Only 60 pulses/sec are produced
Rationale: Half the available x-ray output is lost.
30. Average kVp in single-phase systems?
Answer: One-third of peak kVp
Rationale: Voltage drops to zero between pulses.
, 31. In three-phase systems voltage never drops to?
Answer: Zero
Rationale: Overlapping pulses maintain voltage.
32. Voltage fluctuation is called?
Answer: Ripple
Rationale: Ripple describes variation in kVp.
33. Average voltage in three-phase systems?
Answer: 91%
Rationale: Less ripple increases effective voltage.
34. Increased effective voltage improves what?
Answer: Penetration
Rationale: Higher average energy produces more penetrating beams.
35. Effective mA in three-phase systems is?
Answer: Increased
Rationale: Overlapping pulses increase electron flow.
36. Practical mAs adjustment for three-phase units?
Answer: Reduce by half
Rationale: Increased efficiency requires less exposure.
37. Ripple in a 12-pulse generator?
Answer: 4%
Rationale: Multiple pulses smooth voltage output.
High-Frequency & Power
38. High-frequency generator range?
Answer: 500–25,000 Hz
Rationale: Higher frequency produces near-constant voltage.
39. Why use lower kVp on HF mobiles?
Answer: Average kV ≈ set kVp
Rationale: Minimal ripple increases beam energy.
40. High-mA generators allow what?
Answer: Very short exposure times
Rationale: High mA reduces motion blur.
41. Generator power rating units?
Answer: Kilowatts (kW)
Rationale: Indicates output capacity.
