SENIOR PHYSICS REVIEW
ELECTROMAGNETISM
•	Magnetism – When a charged particle is in motion, a magnetic field perpendicular to the motion will be created.
•	Lines of Flux – Force field created when magnetic dipoles orient to create a magnet.
–	Lines of Flux/Force always flow from north to south outside a magnet and from south to north inside the magnet.
MAGNETIC DIPLOES
•	Atoms having a significant number of electrons with their magnetic moments in the same direction, especially when their outer shells are involved, will exhibit a net magnetic field in a distinct direction.
•	In nonmagnetic objects the magnetic diploes are randomly arranged, essentially cancelling out each other.

MAGNET CLASSIFICATION
•	Classified by type and production.
–	Natural (created when iron oxide remains in Earth’s magnetic field for ages)
–	Artificial Permanent (manufactured from a steel alloy called alnico. Made from aluminum, nickel and cobalt.) al-ni-co “get it”
–	Electromagnets (temporary magnet produced by moving electric current.
CHARACTERISTICS
•	Permeability – the ease in which a material can become magnetized.

•	Retentivity – ability of an material to stay magnetized.

•	Unit or measurement for magnetic fields is the TELSA.
SOLENOIDS/ELECTROMAGNETS
•	Solenoid – when conducting with is looped and a current is applied the magnetic fields from both sides join in the middle and double the magnetic flux density.
•	Electromagnet – If a ferromagnetic core is added inside the loop an electromagnet is created and further increased the flux density. 
DEVICES
•	Generators – converts mechanical energy into electrical energy.
•	Motors - convert electric energy into mechanical energy.
•	Transformers – control electrical current.
–	Primary coil (supplied with current.)
–	Secondary coil (induced by primary.)
•	Step-up Transformer (increases voltage)
•	Step-down Transformer ( decreases voltage) 

AUTOTRANSFORMERS
•	Connects primary and secondary coils in series instead of insulating them.
•	Permits a single coil on a central core.
•	Connections are made a different points for primary and secondary.

BASIC X-RAY CIRCUT
Generators
•	Single-phase 
•	Three-phase 
•	High frequency 
•	Capacitor discharge mobile units
•	Battery-operated mobile units
•	Falling load

Single-Phase Generators
•	Full-wave rectified
–	2 pulses per Hz
–	120 pulses per second
–	Voltage ripple 100%

Three-Phase Generators
•	Full-wave rectified
–	6 pulses per Hz
–	360 pulses per second
–	Voltage ripple 13-25%

Three-Phase Generators
•	Full-wave rectified with 12 diodes
•	12 pulses per Hz
•	720 pulses per second
•	Voltage ripple 4-10%

High Frequency Generators
•	AC and DC power converters and inverters
–	Full-wave rectified unit can produce 12-13 kHz waveform
–	Voltage ripple of 3-4%

Calculation of Heat Units
•	kVp x mA x time x rectification constant

X-RAY PRODUCTION

X-RAY BEAM CHARACTERISTICS

15% Rule
•	Because kVp affects both quality and quantity, a change of only 15% will demonstrate a doubling of film density
Distance (SID)
•	As SID increases, beam intensity decreases
–	And vice versa

Inverse Square Law
•	Intensity of radiation at a given distance from point source is inversely related to the square of the distance between the object and the source

Inverse Square Law
Exposure (Film Density) Maintenance Formula
•	Provides technique correction for change in SID
–	Maintains the same film density

PHOTON INTERACTION WITH MATTER

FLUOROSCOPY

ELECTRONIC (DIGITAL) IMAGING

FILTRATION