Electromagnetism
Natural (lodestones), artificial permanent, and electromagnet
What is a cathode and it's assembly?
The negative side of an x-ray tube. Assembly is the filament, focusing cup, and associated wiring
What is the function of an anode?
It is a target surface so it receives the electrons from the filament and is the source of x-ray photons.
What is a motor?
A device that converts electrical energy into mechanical energy.
What is Faraday's Law (1st Law of Electromagnetism)?
States that four factors regulate the strength of induced current when magnetic lines of force and a conductor are in motion relative to one another.
What are the laws of magnetism?
Repulsion and attraction, Inverse square law, and Magnetic Poles
What is the filament in an x-ray tube made out of and why?
Thoriated tungsten because it has a high melting point and is difficult to vaporize
What is the purpose of the warm-up procedure?
It gradually warms the anode to prevent cracking and helps maintain the vacuum
What is a generator and another name for it?
Device that converts mechanical energy into electrical energy. Also called dynamo.
What is an solenoid?
A coil consisting of a series of loops, which serve to increase the flux density.
What is an electromagnet?
A temporary magnet produced by moving electric current
What are the stator and rotor?
Stator: Induction-motor magnet that turns the anode
Rotor: A copper cylinder connected to anode disk by molybdenum stem that turns when the stator is energized
What is the purpose of the protective housing?
To control leakage and scatter radiation, isolate high voltages, and provide a mean to cool the tube
What does a generator use and why?
Slip rings and brushes, they permit the circuit to remain stationary while the armature rotates without breaking the electrical contact between them.
What are the four factors that the magnitude of induced current depend on?
1. Strength of magnetic field. 2. Speed of the motion between lines of force and the conductor. 3. Angle between magnetic lines of force and conductor. 4. Number of turns in the conducting coil
What is rectification and it's two types?
The process of changing from AC to DC. Solid-state diodes, and vacuum-tube rectifier
An x-ray window is _____ whereas a mammography window is _____?
Glass, beryllium
What is off-focus radiation or extrafocal radiation?
Photons that are not produced at the focal spot and produce "ghosting"
Two types of AC motors? Which is used in x-ray tubes with rotating anodes?
Synchronous and induction. Induction is used in x-ray tubes with rotating anodes.
What is a capacitor?
A device that accumulates and stores electrical charge. The unit is the Farad.
What is retentivity and permeability? What is their relationship?
Retentivity is the ability of a material to stay magnetized. Permeability is the ease with which a material can be magnetized. They are inversely proportional.
What is the focal track?
A circular path that will be impacted by the electron beam.
Ways an x-ray tube can fail
Tube arcing: vaporized tungsten collection on envelop
Filament breakage: filament thinning with age
What is the motor principle?
The result of the interaction of magnetic fields when an electric current is sent along a conductor that is residing in a magnetic field.
What does ferromagnetic, paramagnetic, diamagnetic, and nonmagnetic mean?
Ferromagnetic: Highly permeable and greatly susceptible to induction. Iron, cobalt, nickel
Paramagnetic: Low permeability, have a weak attraction to magnetic fields. Platinum and aluminum
Diamagnetic: Weakly repelled by all magnetic fields. Beryllium, bismuth, and lead.
Nonmagnetic: Not affected by magnetic fields. Wood, glass, rubber, plastic.