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Rectification

rectifiers, etc.

QuestionAnswer
Define rectification. The process of changing alternating current (AC) to pulsating direct current (DC).
What are the 2 methods of rectification? Self rectification; vacuum tube or solid state diode rectification.
Which method of rectification is used in mobile radiography? Self rectification
How are rectifying systems connected? They are connected between the secondary side of the x-ray transformer and the x-ray tube.
What is the most commonly used type of semiconductor? Silicon
Define n-type silicon. Silicon "doped" with arsenic that has an extra electron. (n stands for negative)
P-type Silicon Silicon that contains Gallium and is short of one electron. (P stands for positive)
What device is used to test the competency of rectifiers? Spinning top
What is an oscilloscope? Device used to test the timer in 3-phase, 12-pulse equipment.
Why is arsenic called a "donor atom?" Because it furnishes electrons.
Why is gallium called an "acceptor atom?" Because it can accept electrons.
How many valence electrons are in a silicon atom? 4
How many valance electrons are in gallium's outer shell? 3
Silicon makes use of __________ bonding. Covalent
Where is the rectifier located within the x-ray circuit? Between the secondary side of the x-ray transformer and the x-ray tube.
What is the principle disadvantage of self-rectification? Low heat-loading capacity
T/F: With self-rectification, exposure factors (kV and mAs) must be limited to lower values than with full-wave rectification. True
Half-wave rectification is aka ? One-pulse rectification
What is the spinning top used for? To test the competency of rectifiers with single-phase equipment.
Diode Rectifying semiconductor consisting of a p-type crystal with an n-type to form a p-n junction
Thyristor Silicon-controlled rectifier used for high-speed switching of primary high-voltage x-ray circuit.
Thermionic emission Ejection of electrons from surface of wire due to increased heat, causing an electron cloud
Space charge cloud Same as thermionic emission
What is the main advantage of full-wave rectification? The exposure time for any given technique is cut in half.
Which is more efficient for producing x-rays: Single-phase or 3-phase power? 3-phase
Voltage ripple A way to characterize voltage waveforms.
Single-phase power has __% ripple. 100%
3-phase, 6-pulse power produces __% ripple. 13 - 25
3-phase, 12-pulse power produces __% ripple. 4 - 10
High-frequency generators have approximately __% ripple 1%
Note: Less voltage ripple results in higher radiation quantity and quality
Oscilloscope Used to test the timer in 3-phase, 12-pulse equipment.
What is the effective kVp with 12-pulse generators? 95%
What is the effective kVp with 6-pulse generators? 87%
Which type of rectification will supply the x-ray tube with the greatest power? Full wave
What is the maximum kVp produced by most 3-phase x-ray generators? 150
To produce equal density and contrast, exposure to the patient with 3-phase equipment is ___ compared to single phase. Equally
To prevent shock, the secondary step-up transformer is __. grounded
Why are 3-phase generators more efficient than single-phase generators? Voltage never drop to zero.
Rectifier Device allowing current flow in only one direction.
Star and delta configurations are related to? Three-phase transformers
With 3-phase equipment, toe voltage across the x-ray tube is __ to __% of the maximum value and is nearly ___ potential. 87 to 96%, constant
What is the percentage of voltage ripple for a single-phase generator? 100% voltage ripple
A full-wave rectified, 3-phase, 6-pulse waveform produces approximately ____% more average photon energy than single phase. 35
A full-wave rectified, 3-phase, 12-pulse waveform produces approximately ___% more average photon energy than single phase. 40
Mobile units operate on _______________ battery-supplied AC current. Nickel-cadmium
Created by: rad1958tech on 2008-03-07



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