Unit 5: Filament Circuit

Question 1

what controls the filament temperature?

Answer 1

filament current

Question 2

filament current is measured in _____

Answer 2

amperes (A)

Question 3

What is the typical range of current for the filament current?

Answer 3

3-6 amperes (A)

Question 4

as filament current increases, the filament gets _______ and more electrons are released by ______________

Answer 4

hotter; thermionic emission

Question 5

where does the filament circuit receive its voltage from?

Question 6

what is tube current?

Answer 6

quantity of electrons available to travel from cathode to anode during exposure

Question 7

what monitors tube current?

Answer 7

the mA meter

Question 8

what controls tube current?

Answer 8

the filament circuit

Question 9

what is the rheostat?

Answer 9

a highly precise variable resistor

Question 10

what does the rheostat do?

Answer 10

it adjusts the levels of voltage coming from the autotransformer after mA selection

Question 11

what does the rheostat control?

Answer 11

the amount of voltage sent to the primary side of the step-down transformer

Question 12

what type of transformer is located in the filament circuit?

Answer 12

step-down transformer

Question 13

what does the step-down transformer do?

Answer 13

it decreases the voltage so that there is necessary current for thermionic emission at the filament

Question 14

what happens at the filament when there is a decrease in voltage and an increase in current?

Answer 14

the filament will reach higher levels, causing more electrons to be burned off through thermionic emission

Question 15

what does the exposure timer do?

where is it most always done at?

Answer 15

it “makes” and “breaks” the high voltage across the x-ray tube

on the primary side of the high-voltage transformer where the voltage is lower

Question 16

list the three types of exposure timers:

Answer 16

electronic
mAs
AEC

Question 17

which is the most accurate type of exposure timer?

Answer 17

electronic

Question 18

what can electronic timers be used for?

Answer 18

rapid serial exposures and are suitable for IR

Question 19

what do mAs timers do?

Answer 19

they monitor the product of mA and exposure time and terminates exposure when desired mAs is attained

Question 20

where are mAs timers located?

Answer 20

on the secondary side of the high-voltage transformer

Question 21

when does the AEC terminate the exposure?

Answer 21

when the image receptor has received the required radiation intensity

Question 22

AEC incorporates a flat, parallel ___________________ positioned between the _______ and the _______

Answer 22

ionization chamber; patient; IR

Question 23

when radiographs are taken in the AEC mode, the electronic timer should be set to ________ the expected exposure time as a back up timer

Answer 23

1.5 times

Question 24

the AEC has how many cells?

Answer 24

3; one middle and two outer