Exam 2 ch. 5-7 Flashcards
(Ch 5) Velocity
symbol: v
how fast energy oof wave moves from one point to another
radiology measured in seconds (meters/second)
(Ch 5) Amplitude
the strength of the wave (not the energy)
maximum displacement of media from its equilibrium
(Ch 5) wavelength
Symbol: (lambda) λ
distance between two like points (crest to crest) constitutes one cycle
measure in angstroms
xray range .1-.5
(Ch 5) frequency
Symbol: f –
Measured in Hertz (Hz)
The number of cycles that pass a
fixed point in a second.
(Ch 5) Velocity triangle
V = Fλ
λ= v/f
f=v/λ
(Ch 5) what is frequency and wavelengths relationship?
NVERSELY PROPRTIONAL relationship
When frequency increases, wavelength must decrease if velocity is constant.
(Ch 5) electromagnetic wave formula
All electromagnetic waves travel at the speed of LIGHT (in a vacuum)
If frequency goes up, wavelength goes down (is shorter)
Energy is directly proportional to FREQUENCY
(Ch 5) Resonance
The tendency of electromagnetic radiation to interact with substances that have a natural frequency similar to theirs
(Ch 5) visible light
reflect
refract
disperse
absorb
(Ch 5) high energies behave like:
PARTICLES
(Ch 5) x-rays
about the highest energy you can get
do not reflect
do not refract
do not disperse
but do absorb
(Ch 5) X-rays with absorbtion
X-rays with low energy
X-rays that interact with radiopaque objects
(Ch 5) x-rays that transmission
X-rays with high energy
X-rays that do not interact with radiopaque objects.
(Ch 5) what kind of nature do x-rays have?
dual nature
They have qualities of both light photons and physical particles.
(Ch 5) What is attenuation?
The partial absorption of light or x-rays
(Ch 5) what is radiolucent?
x-rays can pass easily
ex: air
(Ch 6) MAGNETIC MOMENT
The orientation of the magnetic field for a single electron or proton
(Ch 5) What is radiopaque?
allowing very few x-rays to pass
ex: jewelry, bones, leads
(Ch 6) electromagnetism
all moving electric charges develop magnetic fields
(Ch 6) MAGNETIC DIPOLE
The small magnetic field around an entire atom
(Ch 6) MAGNETIC DOMAIN
A group of atoms that all have their magnetic dipoles pointed in the same direction
(Ch 6) FERROMAGNETIC (materials)
Materials such as iron and nickel that allow their magnetic domains to be easily lined up in the same direction when subjected to a strong external magnetic field.
(Ch 6) PARAMAGNETIC (materials)
Materials that are only slightly attracted to magnetic fields (Al, O, Au, Cu)
(Ch 6) DIAMAGNETIC (materials)
Materials that lightly repel a magnetic field (glass, water
(Ch 6) NON-MAGNETIC (materials)
All other materials that are unaffected by magnetic fields (wood, rubber)
(Ch 6) RETENTIVITY (materials)
The ability of a magnet to hold on to its magnetism over time
(Ch 6) Magnetic fields
Magnetic fields are strongest near the POLES
(Ch 6) 1 gauss is equal to?
Roughly the strength of earth’ magnetic field at the POLES
(Ch 6) What does magnetic fields follow?
The strength of the attraction / repulsion of poles follows the INVERSE SQUARE LAW
(Ch 6) Tesla is equal to?
Equal to 10,000 Gauss. Typical strength of a medical MRI machine is 2T
(Ch 6) Laws of electro-statistics
Like charges repel, opposites charges ATTRACT.
In solid objects, only electrons MOVE.
In solid objects, free electrons only exist on the SURFACE.
In solid objects, free electrons concentrate near the point of greatest CURVATURE.
(Ch 6) What is electrostatistics?
studies the slow moving or stationary electric charges
The unit of electrical charge is the Coulomb
(Ch 6) What is static electricity? (electrification)
is cause by electrification by friction
ex: shoveling feet collecting electrons
(Ch 6) What is electrification?
(Ch 6) Contact (electrification)
Occurs when a potential difference (charge) exists between two objects that touch each other.
(Ch 6) Induction (electrification)
A charge is induced in another object without touching it
(ex a transformer moving a smaller transformer in and out of the magnetic field)
(Ch 6) Electromotive force: (electrification)
The force created by any electric potential difference. Unit: VOLT
(Ch 7) What is electrodynamics?
(Ch 7) Electrical current can only flow through certain materials:
Conductors – Electrical current flow in most conditions
Semiconductors – Electrical current flow in certain conditions
Insulators – No electrical current flow
(Ch 7) Current:
The flow of loosely-bound, outer shell electrons
Unit: The Ampere or Amp, abbreviated “A” or “I” and defined as 1 Coulomb per second
EX: (outer electrons move on the top in one direction then current MUST move in the opposite direction)
(Ch 7) SERIES Circuit (pictures will be on exam)
Each component of the circuit is connected to each other.
A failure of one component breaks the circuit
EX: Christmas lights
(Ch 7) PARALLEL Circuit (pictures will be on exam)
Each component is connected to the power source independently.
A failure of one component only breaks the circuit to that component, not the others.
(Ch 7) Resistance
How much force is preventing the electrons from moving through a circuit
(Ch 7) Resistance is affected by:
Length of conductor (A lot of R ——- not much R –)
b. Diameter of conductor (O o think firehose & water)
c. Conducting material (Rubber: bad Copper: good)
(Ch 7) Ohms Law
V=IR
Also a triangle for this law
I=v/r
R=v/I
(Ch 7) Ohms law pyramid:
V= volts
I= amperage (amps)
R= ohms
(Ch 7) Velocity pyramid:
V= velocity (m/s)
f= frequency (hz)
λ= wavelength (meters)
(Ch 7) Three ways to generate alternating current:
Move a conductor back and forth through a magnetic field.
Move a magnetic field back and forth near a conductor.
Alternate the strength of a magnetic field.
(Ch 7) Electrical power
The RATE at which electrical power is used
UNIT: The Watt (W)
(Ch 7) Alternating current
Oscillation of current back and forth
At a frequency of 60-Hertz each cycle lasts for 1/60th second
(a graph with a line and waves going above and below this line best demonstrates the forward and back movements)
(Ch 7) Transformers
Transformers use induction to transform:
Voltage
Amperage
(Ch 7) Induction only works with:
Alternating Current
(Ch 7) The secondary coil of a transformer has 20,000 turns and the primary coil has 500 turns.
What is the ratio
40 to 1
Step up
voltage x 40
amp x 40
(Ch 7)
(Ch 7) AUTOTRANSFORMER
Uses the concept of self-induction to slightly change the voltage in a circuit.
