Lesson 2

Question 1

Rectification

Answer 1

process where a AC is changed to DC (oscillating to pulsating)

Question 2

Rectifier

Answer 2

an electronic device that allows electron current to go in one direction. There’s a high resistance to move in the other direction.

Question 3

X-ray tubes use DC because when using AC the flow of electrons can move in the ______ direction and ______ the tube.

Answer 3

wrong , damage

Question 4

diode

Answer 4

a device with 2 electrodes

Question 5

what is the symbol for a diode?

Answer 5

an arrowhead that points in the direction of the current

Question 6

What are diodes typically made of?

Answer 6

semiconductors like silicon

Question 7

What are the 2 types of semiconductors?

Answer 7

N-type and P-type

Question 8

N-type semiconductors

Answer 8

have loosely bound electrons free to move

Question 9

P-type semiconductors

Answer 9

positive electron traps (holes)

Question 10

n-type + p-type = ?

Electrons are allowed to flow in?

Answer 10

p-n junction

only in one direction

Question 11

“forward bias” p-n junction

Answer 11

current is allowed to flow as holes and electrons go toward each other reducing the barrier voltage

Question 12

“reverse bias” p-n junction

Answer 12

current flow is prevented as electrons and holes move away from each other and the barrier voltage increases

Question 13

Disadvantage of Self-Rectification?

Answer 13

low heat loading capacity of a x-ray tube. The anode can easily overheat.

Question 14

self-rectification

Answer 14

when no rectifier is used and the x-ray tube acts as the “valve tube/diode”

Question 15

Half-wave rectification

Answer 15

“one-pulse” (only positive)
1 voltage peak per cycle (1/2 a normal cycle)
60 pulses per 60 Hz
inefficient- negative half cycle wasted

Question 16

Full-wave rectification

Answer 16

“two-pulse” (both positive and negative)
2 voltage peaks per cycle (a normal cycle)
120 pulses per 60 Hz
more efficient - reverses negative half cycle

Question 17

Full Rectification Advantage

_______ in the power output capability of equipment. Results in ________ __________.

Answer 17

Increase , larger exposures

Question 18

Full Rectification Disadvantage

_____ percentage of low energy x-rays

Answer 18

high

Question 19

radiographic underexposure

Answer 19

one rectifier fails (full wave / 4 rectifiers goes to a two-diode half wave)

Question 20

3 phase power

Answer 20

multiple voltage waveforms superimposed for a constant high voltage

Question 21

3 phase , 6 pulse

Answer 21

ripple of 13-25%
voltage never drops below 75-87%
35% more “average energy” photons than single phase

Question 22

3 phase , 12 pulse (diodes)

Answer 22

ripple of 4-10%
voltage never drops below 90-96%
40% more “average energy” photons than single phase

Question 23

What is the kV ripple for single phase 2 pulse?

Answer 23

100%

Question 24

High Frequency (________)

Generators use AC and DC power converters to change the incoming line from ____ to _____.

peak kV is achieved in about ____ of the time needed for 3 phase generators.

What is the kV ripple?

Answer 24

Line Voltage

60 Hz to 6000 Hz

10%

3-4%

Question 25

Advantages of 3 phase power when compared to single phase?

Answer 25

the lower voltage ripple gives more efficient radiation less low energy x-rays greater tube capacity

Question 26

Motor Principle

Answer 26

involves the interaction of magnetic fields from a wire with an electric current. There is a force on the wire that pushes it out the field.

Question 27

Galvanometer

Answer 27

measures current and voltage, made of copper wire wrapped around a horseshoe magnet

Question 28

Ammeter

Answer 28

connected in series and used to measure current

Question 29

Voltmeter

Answer 29

connected in parallel and measures potential difference

Question 30

What are the protective devices used to prevent a short circuit fire?

Answer 30

ground , fuses , circuit breakers

Question 31

Ground

Answer 31

equipment is grounded to the earth to protect x-ray specialist and patient from shock. In a socket typically one hole is for ground, one neutral , and one live)

Question 32

Fuses

Answer 32

connected in a series and is not reusable. The metal tab inside melts to end the flow of electrons.

Question 33

circuit breakers

Answer 33

pop open once a temperature is reached and can be reused of reset. involves bimetallic strips bending.

Question 34

Autotransformer Law Formula

Answer 34

Vs / Vp (s nd p are subscripts) ``` # tapped turns ____________ ``` primary turns

Question 35

Variable resistor is also know as ?

Answer 35

Rheostat or potentiometer

Question 36

Variable resistor

Answer 36

Determines how much resistance by manipulating voltage and current

Question 37

Auto transformer

Answer 37

Controls the low voltage side on X-ray circuit