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RTE 1041 - Radiographic Equipment & Imaging I > Chapter 8 - X-Ray Machine Circuits and Generators > Flashcards

Chapter 8 - X-Ray Machine Circuits and Generators Flashcards

1
Q

What are the 3 general sections of the main x-ray circuit?

A
  • control console
  • high-voltage section
  • x-ray tube circuit
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2
Q

What is a line-voltage compensator?

A

device that measures fluctuating incoming voltage from the power line and automatically compensates by adjusting the autotransformer slightly up or down to maintain uniform, accurate voltage

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3
Q

What is the typical turns ratio range for the high voltage step-up transformer?

A

500:1 - 1000:1

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4
Q

What are the 3 general types of exposure timers for manually set techniques? What is the most common?

A
  • synchronous
  • electronic (most common)
  • mAs
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5
Q

In the high-voltage x-ray machine circuit, what is the very last thing that must be done with the electrical current before it reaches the x-ray tube?

A

IT MUST BE RECTIFIED SO ELECTRONS ALWAYS ENTER THE TUBE IN THE SAME DIRECTION

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6
Q

The step-up transformer is between the _____ and the _____.

A

AUTOTRANSFORMER
RECTIFICATION BRIDGE

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7
Q

The step-down transformer is between the _____ and the _____.

A

RHEOSTAT
X-RAY TUBE FILAMENT

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8
Q

What is the typical range of output voltage from the autotransformer?

A

100 - 400 volts

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9
Q

What is the typical turns ratio for the step-down transformer in the filament circuit?

A

1:44

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10
Q

In a solid-state diode, if electrons drift in n-type silicon, what drifts in p-type silicon?

A

HOLES

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11
Q

Why can’t electricity pass backward through the solid-state diode?

A

WHEN AC CURRENT REVERSES DIRECTION, THE ELECTRONS AND HOLES ARE NO LONGER REPELLED TO THE N-P JUNCTION AND THE POTENTIAL BRIDGE DISCONNECTS

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12
Q

Why is high amperage, rather than high voltage, needed for heating of the filament?

A

HIGH AMPERAGE CREATES GREATER FRICTION WHICH EMITS HEAT

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13
Q

After depressing the exposure switch all the way, why does the x-ray machine prevent any exposure until the “ready” light comes on?

A

THE FILAMENT NEEDS A FEW SECONDS TO HEAT UP FROM THE HIGH-AMPERAGE CURRENT

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14
Q

On most x-ray machines, when the mA station is selected, what particular type of electrical device in the circuit is being selected?

A

A RESISTOR IN THE RHEOSTAT

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15
Q

When the kVp is selected, what electrical device is being adjusted?

A

THE AUTOTRANSFORMER

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16
Q

Voltage meters must be connected in which way in the circuit?

A

IN PARALLEL

17
Q

Does the mA meter measure the filament current or the tube current?

A

TUBE CURRENT

18
Q

What is defined as the “boiling off” of electrons from a heated filament wire?

A

THERMIONIC EMISSION

19
Q

Why is self-rectification dangerous to the x-ray tube?

A

THE ELECTRONS CAN MOVE BAKWARDS FROM ANODE TO CATHODE AND DAMAGE THE FILAMENT

20
Q

Compared with a 1 phase machine, radiographic techniques can generally be changed by how much for 3 phase and high-frequency machines?

A

THEY CAN BE HALVED

21
Q

Higher-power generators are more efficient because they have a lower percentage of what effect in their waveform?

A

RIPPLE

22
Q

What is the only logical way for the radiographer to modify the exposure intensity while the AEC is engaged?

A

ADJUST THE DENSITY CONTROL

23
Q

Why does the AEC take longer to shut off the exposure when the patient is rolled up onto his/her side, or when a thicker patient is placed in the beam?

A

THE RATE OF X-RAYS REACHING THE DETECTORS IS REDUCED, SO CHARGING THE CAPACITOR TAKES LONGER

24
Q

When setting the density control, what specific electrical device is being adjusted?

A

THE THYRATRON

25
Q

What are the 3 main components of the high-voltage circuit on an x-ray machine?

A
  • autotransformer
  • step-up transformer
  • rectifier bridge
26
Q

What are the 2 main components of the filament circuit?

A
  • resistor bank (rheostat)
  • step-down transformer
27
Q

How many rectifying diodes are at minimum required for full-wave rectification?

A

4

28
Q

What percentage of the kVp setting is actually generated as kilovoltage in each of these generators?

  • 1 pulse
  • 3 phase, 6 pulse
  • 3 phase, 12 pulse
  • high-frequency
A
  • 33%
  • 91%
  • 97%
  • 99%
29
Q

How is the power rating for an x-ray machine calculated?

A
  • (max mA)(kVp)/1000
  • expressed in kW
  • multiply mA and kVp by 0.7 for single phase machines
30
Q

How does an electronic timer work?

A

charge is accumulated and stored on a capacitor until a preset limit is reached, the the capacitor discharges electricity to trip a switch

RTE 1041 - Radiographic Equipment & Imaging I (11 decks)

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