physics chapter 4 part 2 Flashcards Preview

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Flashcards in physics chapter 4 part 2 Deck (47)
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Parts of the primary circuit

Consists if the main power switch(connected to incoming power supply), circuit breakers, the auto transformer, the timer circuit, and the primary side of the step up transformer


Parts of the secondary circuit

Secondary side of step up transformer, the milliamperage meter, a rectifier bank, and the X-ray tube


Parts of the filament circuit

Rheostat, step down transformer and the filaments


Know what causes the pulsation in a single phase circuit

The alternating change in voltage from zero to maximum potential 120 times each second in a full wave rectified circuit


Know how a 3 phase circuit or 3 phase power works

Six pulse circuit requires 6 rectifies to produce six usable pulses per cycle, 12 pulse circuit requires 12 rectifies to produce 12 useable pulses per cycle


What does the 3 phase provide?

More efficient xray production


Know what the end result will be for 3 phase

Wave form which never reaches zero, thereby providing an increased voltage


Why circuit breakers are included within a circuit

To protect against short circuits and electric shock


What are auto transformers

An adjustable transformer controlled by the kilovoltage peak selector on the operating console


How does the radiographer control the autotransformer

When radiographer selects a kVp setting


What does the autotransformer operates under?

Principle of self induction


Why is an autotransformer sometimes balled kVp selector

Because of its function


What's an autotransformers primary purpose

To provide a voltage that will bE increased by the step up transformer to produce the kilovoltage selected at the operating console


What does the step up transformer in the primary circuit change?

◾️increase voltage from autotansformer to kVp necessary for xray production
◾️alternating current from low voltage to high voltage


What is the step up transformer in the primary circuit a dividing line of?

Between the primary and secondary circuits


Where the 2 parts of the step up transformer in the primary circuit are located?

◾️primary coil ➡️ primary circuit
◾️secondary coil➡️secondary circuit


How does the step up transformer differ from the autotansformer

This transformer is not adjustable and increase the voltage from the autotransformer by a fixed amount


Why is the exposure timer located in the primary circuit?

It's easier to control (turn in or off) a low voltage than a very high one


First variation of timer and explain it

Synchronous timer➡️ based on a synchronous meter


Second variation of timer and explain it

Electronic timer➡️ very sophisticated and accurate timer that is most widely used today based on the time it takes to charge a capacitor.


Third variation of timer and explain it

mAs timer- variation of electronic timer, but it monitors the current passing through the X-ray tube and terminates the exposure when the desired mAs is reached. Located in the secondary circuit.


Know how the aec works differently than an exposure timer

Uses the patient body part of interest as the variable in determining when to terminate exposure. AEC uses a device called the ionization chamber.


What AEC controls

Only the quantity of radiation reaching the IR and therefore has no effect on other image characteristics such as contrast


Know what secondary circuit begins with

The rest of the step up transformer


Know what the milliampere meter is

A device placed in the secondary circuit that monitors X-ray tube current


Know where and why the tube is grounded

To prevent electrical shock ➡️ secondary circuit


What rectifiers are

Convert AC ➡️ DC allows current to flow from anode ➡️ cathode and electrons from cathode to anode. Made of two semi-conducting crystals


Which rectifiers are commonly used today

Solid state rectifier


How we get the best use of rectifiers

Arranged in pairs so that the AC cycle has an open "path" from each direction


Know the type of current needed for transformer



What current must supply X-ray tube



Know how the current flows inside X-ray tube

Anode ➡️ cathode


Know what the symbol means and stands for

Solid state rectifiers/diode
Current flow is with the direction of the arrow and electron flow is against the arrow


Define half-wave rectification

When only two rectifiers are used and only one half of the AC cycle flows through the xray and the other half is suppressed


Define full-wave rectification

When four rectifiers are used and both halves of the AC are used.
•By using four rectifiers & arranging them in specific way, both halves of the AC are used
•Resulting waveform is illustrated
•In effect, we “invert” the negative half of the cycle, thereby making use of the entire cycle


Define ripple

Measures the amount of variation between maximum and minimum voltage


Know what filament circuit begins with



Define milliampere parameter

(Tube current) it reflects the rate of flow of electrons passing through the X-ray tube during exposure


Be able to describe what happens when you adjust milliamperage on operating console

You are adjusting the rheostat and the amount of resistance in the filament circuit and ultimately the amount of current applied to the filament in the X-ray tube.


Know the relationship between milliamperage and resistance

Higher milliamperage lower the resistance


Know the goal of the filament circuit

Literally boil electrons out of the filament wire


What would happen in the filament circuit if the current gets too high

The tiny wire will be damaged or destroyed


What's the role of the rheostat in the filament circuit

Controls filament temperature and the rate at which electrons are boiled off of the filament


What's the role of the timer in the filament circuit

Determines the duration of this process


What's the role of the step down transformer In the filament circuit

Used in the filament circuit to increase the current by reducing the voltage that is applied to the filament


Know the purpose if the filament circuit

To control the degree to duration that the filament is heated, which in turn controls the number of electrons boiled off that will ultimately become the tube current


Know how the filaments are represented in the console

Large focal spot and small focal spot