RTE1418 Imaging - Unit 4 Electromagnetism

  1. A fundamental force in nature that gives some forms of matter the ability to attract other forms of matter, such as iron
    Magnetism
  2. In 1600, English scientist ____ ____ confirmed earlier observations regarding magnetic poles and concluded that the Earth was a magnet.
    William Gilbert
  3. ___ ___ ___ - created when electrons orbits the nucleus in a closed loop
    Orbital magnetic moment
  4. ___ ___ ___ - created when electrons spin on their axis (protons in the nucleus also exhibit this property - basis of MRI)
    Spin magnetic moment
  5. The small magnet created by an electron in orbit called a?
    magnetic dipole
  6. Groups of many atoms with their dipoles aligned created a?
    magnetic domain
  7. Magnetic fields are referred to in terms of lines of force or?
    Lines of Flux
  8. The number & concentration of the lines of flux in an area determines the strength of the magnetic field and magnet called?
    flux density
  9. the SI unit for measuring field strength (flux density) is ___?
    the Tesla (T)
  10. Serbian-American inventor, electrical engineer, mechanical engineer, physicist, and futurist who is best known for describing rotating magnetic fields in 1882 & later developing AC electrical systems.
    Nicola Tesla
  11. The 3 Magnetic Classifications are?
    1. Natural - those created within the earth

    2. Artificial permanent - those manufactured out of metal alloys

    3. Electromagnets - temporary magnets produced by moving electric current
  12. Artificial Permanent Magnet
    What is ALNICO?
    an alloy of Aluminum, Nickel, and Cobalt
  13. What 3 things make up the Laws of Magnetism.
    • 1. Repulsion-attraction
    • - Like poles repel; unlike poles attract

    • 2. Inverse Square Law
    • -The force between 2 magnetic fields is directly proportional to the product of their magnitudes & inversely proportional to the square of the distance between them.

    • 3. Magnetic Poles
    • - Every magnet has 2 poles, North and South. 
    • - If you divide a magnet it creates 2 magnets - each with a North and South pole
  14. ____ - the ease in which a material can be magnetized
    Permeabilty
  15. ___ - the ability of a material to stay magnetized
    Retentivity
  16. The 4 Magnetic Classifications of Materials are?
    • 1. Ferromagnetic - materials that are strongly attracted to magnets and magnetic fields
    • Ex: Iron, nickel, and cobalt

    • 2. Nonmagnetic - materials not affected by magnets or magnetic fields
    • Ex: Wood, glass, rubber, and plastics

    • 3. Paramagnetic - materials weakly attracted to magnets and magnetic fields.
    • Ex: Platinum, aluminum, and magnesium

    • 4. Diamagnetic - materials weakly repelled by magnets and magnetic fields. 
    • Ex: copper, silver, lead, and gold.
  17. Electricity & Magnetism can be thought as different aspects of the same force: _____
    Electromagnetism
  18. Danish chemist & physicist who first demonstrated in 1820 that electric currents created magnetic fields. Experiment with an electrical wire and a compass.
    Hans Oersted
  19. What was the Right-Hand Rule, and who created it?
    The right-hand rule describes the direction of the current and magnetic fields along a conducting wire. 

    This rule was created by English scientist John Fleming)
  20. When a conducting wire is looped and electric current passed through it, a _____ is created.
    solenoid
  21. A _____ is a solenoid with a ferromagnetic material  (such as an iron bar) added to the center. This increased the magnetic strength further.
    electromagnet
  22. The strength of a solenoid or electromagnet depends on what 3 things?
    1. The number of loops (turns) of wire

    2. The strength of the electric current passed through it

    3. The permeability of the core


    - Solenoids & electromagnets are used for detents and other locks on radiographic equipment.
  23. ____ ____ is the production of an electric current in a conductor by a changing magnetic field.
    Electromagnetic induction
  24. English scientist who described the principles of electromagnetic induction in 1831.
    Michal Faraday
  25. Faraday's Law: The 4 factors that regulate the strength of induced current are?
    1. The strength of the magnetic field

    2. The speed of motion between the line of flux and the conductor

    3. The angle between the magnetic lines of force and the conductor

    4. The number of turns in the conducting coil
  26. Induction of current in a secondary coil by applying a varied current through a primary coil - is an example of what?
    Mutual induction
  27. Induction of an opposing voltage in a single coil by its own changing magnetic field: is an example of?
    Self induction
  28. ____ - Devices that convert mechanical energy into electrical energy through principles of electromagnetic induction.
    Generators
  29. ___ - Devices that convert electrical energy into mechanical energy (motion)
    Motors
  30. Rotor - bars of copper around an iron core
    and 
    Stator - electromagnets arranged around the rotor
    together make up a type of ____ ____
    Induction motor
  31. The 3 factors of controlling Electricity are?
    1. Transformers

    2. Autotransformers

    3. Capacitors
  32. ____ - Devices used to change the magnitude of voltage in an AC circuit
    Transformers
  33. ___ ___ transformers convert lower AC voltages into higher AC voltage
    • Step-up
    • - has more turns in the secondary coil than is found in the primary coil
  34. ___ ___ transformers convert higher AC voltages into lower AC voltage
    • Step-down
    • - has less turns in the secondary coil than is found in the primary coil
  35. ____ ____ - voltage change across a transformer is directly proportional to the number of turns
    Transformer Law
  36. Name the 4 types of Transformer configurations.
    1. Air Core - a simple transformer

    2. Open-core

    3. Closed-core

    4. Shell type
  37. ____ - A variable transformer that can act as a step-up or a step-down transformer.
    Autotransformer
  38. The 3 types of transformers in x-ray machines are?
    1. Autotransformer - used to vary the incoming line voltage sent to the high-voltage step-up transformer

    2. Step-up transformer - used to raise the incoming line voltage to kilovoltage (kV) needed for x-ray production

    3. Step-down transformer - used to decrease the incoming line voltage needed to heat the x-ray filaments and produce electrons (filament circuit/mA)
  39. ____ - Devices used to accumulate & store electric charges
    Capacitors
  40. ____ - The process of changing AC into pulsating DC
    Rectification
  41. Most common type of rectifier in x-ray machines: ?
    solid-state semiconductor diodes
  42. ___ ___: the negative portion of the AC cycle is suppressed by the flow of electrons
    Half-wave
  43. ___ ___: the negative portion of the AC cycle is changed to positive
    Full wave
Author
Marc817
ID
345389
Card Set
RTE1418 Imaging - Unit 4 Electromagnetism
Description
RTE1418 Imaging 1 - Unit 4 Electromagnetism
Updated