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Physics > Rad Review Jerry's Questions > Flashcards

Rad Review Jerry's Questions Flashcards

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1
Q

The formula for determining the heat units for a 3-phase, 6-pulse x0ray generator is?

A

kV x time x mA x 1.35

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2
Q

The voltmeter, which reads the kVp selected, is located where in the radiographic circuit?

A

Between the autotransformer and step-up transformer

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3
Q

How many rectifiers are required for a full-wave, 3-phase, 12-pulse x-ray generator?

A

Twelve

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4
Q

During fluoroscopy, what is the range of mA used in the x-ray tube?

A

0.5-5 mA

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5
Q

An exposure is taken with a spinning top on a single-phase, fully rectified x-ray generator at an exposure time of 1/30 sec. If the timer circuit is working properly, the radiograph should yield?

A

4 dots

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6
Q

Why is it important for the x-ray tube to have a vacuum inside it?

A

This allows electrons to flow without any impedance

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7
Q

A tube chart is used to

A

Provide a safe range of exposure factors that may be utilized

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8
Q

Calculate the amount of heat units for the following single-phase, fully rectified unit
70 kVp; large focal spot; 8:1 portable grid; 20 mAs; 0.10 sec; 72” SID

A

1400 HU

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9
Q

Which of the following methods are used to regulate the amount of thermionic emission that occurs at the filament?

A

Variable resistor

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10
Q

Calculate the total resistance for the following circuit if the resisitors are connected in parallel.
5 ohms, 5 ohms, 20 ohms, 30 ohms

A

2.07 ohms

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11
Q

Calculate power for the following series circuit:

20 amps, 3 resistores of 5 ohms, 3 ohms, and 6 ohms

A

5600 Watts

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12
Q

How long does it take for the completion of one sine wave representing 60 hertz of current?

A

1/60 seconds

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13
Q

According to the low of conservation of energy, voltage and amperage have which type of relationship across a transformer?

A

Inversely proportional to each other

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14
Q

In the image intensifier, the anode serves to

A

Accelerate the electrons across the tube

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15
Q

What component in the image intensifier allows images to be magnified?

A

Electrostatic focusing lens

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16
Q

An x-ray tube has a heat storage capacity of 500,000 HU. How many rapid sequence exposures can be made at the following factors, before exceeding the capacity?
200 mA, 80 kVp, 0.4 sec, 30”SID

A

78

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17
Q

The inverse square law relationship between intensity and distance from a source is based upon

A

Divergence

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18
Q

Photomulitplers, thyratrons, and ionization chambers are devices used in

A

Automatic exposure devices

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19
Q

The size of an object is 7”. The SID is 40”. The OID is 9”. What is the resultant size of the image?

A

9.03”

20
Q

When electrons approach the positive electrostatic field of the target, they are abruptly decelerated and lose energy. This energy is converted to

A

Bremsstrahlung radiation

21
Q

In the usual diagnositc kV range, insofar as energy absorption from the beam is concerned, which type of interaction between radiation and matter predominates?

A

Photoelectric effect

22
Q

In the x-ray circuit, the current flowing between the rectifier and the tube is

A

Pulsating DC

23
Q

In the exposure from an x-ray tube is 400 mR at a distance of 36 inches, what will the new exposure be at 50 inches using the same technique?

A

207 mR

24
Q

Which of the following statements is/are correct regarding the anode?
I. It is the positive pole
II. The electron cloud forms here
III. It may be stationary or rotating

A

I and III

25
Q

Minification gain occurs when

A

Electrons from the photocathode converge on the output screen

26
Q

A radiographic unit that requires an oscilloscope to detect voltage waveform irregularities would be

A

A 3-phase, 12-pulse unit

27
Q

The thickness of the tomographic section is determined by

A

Exposure angle

28
Q

The compton effect is characterized by

A

Part transfer of energy upon collision

29
Q

Gamma and x-radiation are the same in every way except

A

both do not have the same origin

30
Q

A radioactive source has a half-life of 7 hours. How many hours are required to reduce a 84-millicurie/hr. dose to a level of 5.25 milicuries/hr?

A

28 hours

31
Q

The basic reqard of the air-gap technique, improved contrast, relies on the following principle

A

Due to increased OID, the angle of the scatter will miss the film

32
Q

The M shell orbit in atomic formation is able to contain a maximum of

A

18 electrons

33
Q

X-rays produced from the movement of electrons from an outer shell to an inner shell is termed

A

Characteristic radiation

34
Q

The incident photon gives up all its energy to cause excitation; a new photon of the same energy is given off in a random direction

A

Unmodified scatter

35
Q

Produces an ion pair

A

Photoelectric effect and compton scatter

36
Q

Is responsible for true absorption

A

Photoelectric effect

37
Q

Is responsible for scattered radiation causing fogged film

A

Compton scatter

38
Q

Causes ionization in tissue

A

Photoelectric effect and compton scatter

39
Q

Concerned with only in therapy ranges of 1.02 or greater

A

Photodisintergration

40
Q

Incident photon with KeV greater than but close to the binding energy of outer shell electrons. Atomic number is high to increase probability.

A

Photoelectric effect

41
Q

Incident photon with KeV considerably greater than the binding energy of outer shell electrons

A

Compton scatter

42
Q

Results in true secondary radiation and energues characteristic of the binding energies of the shells involved

A

Photoelectric effect

43
Q

What is the efficiency of x-ray production, using a tungsten anode, at 90 kVp?

A

0.675%

44
Q

Faraday’s Law is also referred to as the

A

Law of Electromagnetic Induction

45
Q

During a fluoroscopic procedure, the radiologist selects a smaller field-of-view, resulting in a magnified image on the TV monitor. How does this affect the amount of radiation that the patient receives?

A

It increases the amount of radiation the patient receives

Physics (5 decks)

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