Test 2 Review Flashcards
Velocity
How fast energy of wave moves from one point to another
Amplitude
Maximum displacement of media from its equilibrium
Strength of wave, not its energy
Wavelength
Distance between two like points on wave
Measured in Angstroms
Angstrom = 10^ -10 m
Frequency
Number of cycles passing a fixed point in a second
Measured in Hertz
Velocity equals ___ x ___
frequency
wavelength
Frequency & wavelength have ___ proportional relationship
inverse
Electromagnetic wave formula
c = frequency x wavelength
c = speed of light
All electromagnetic waves travel at speed of light (in vacuum)
If frequency increases, wavelength decreases
Energy is directly proportional to frequency
Energy is ___ proportional to frequency
directly
Energy is directly proportional to ___
frequency
Resonance
Tendency of electromagnetic radiation to interact w/ substances having similar natural frequency
X-rays have ___ nature
dual
Qualities of both light photons and physical properties
High energies behave like ___
particles
Reflection: Light vs. X-ray
Light: yes
X-ray: no
Refraction: Light vs. X-ray
Light: yes
X-ray: no
Dispersion: Light vs. X-ray
Light: yes
X-ray: no
Absorption: Light vs. X-ray
Light: yes
X-ray: yes
Low energy X-rays
X-rays that interact w/ radiopaque objects
Transmission: Light vs. X-ray
Light: yes
X-ray: yes
High energy X-rays
X-rays that interact w/ radiolucent objects
Attenuation
Partial absorption of light or X-rays
Radiopaque
Very few X-rays pass thru
Radiolucent
X-rays can pass easily thru
Electromagnetism
All moving electric charges develop magnetic fields
Magnetic moment
Orientation of magnetic field for single electron or proton
Magnetic dipole
Small magnetic field around entire atom
Magnetic domain
Group of atoms w/ magnetic dipoles pointed in same direction
Ferromagnetic
Iron/nickel materials w/ magnetic domains easily lined up in same direction
Paramagnetic
Materials slightly attracted to magnetic fields
Al, O, Au, Cu
Diamagnetic
Materials slightly repel magnetic field
Glass, water
Non-magnetic
Materials unaffected by magnetic field
Wood, rubber
Retentivity
Ability of magnet to hold on to its magnetism over time
Magnetic fields are strongest near the ___
poles
Strength of attraction/repulsion of poles follows the ___ law
Inverse square law
Magnetic field - unit of measurement
Gauss (G) - roughly strength of earth’s magnetic field at the poles
Tesla (T) equals ___ gauss
10,000
Typical strength of MRI machine
2 Teslas (T)
Electrostatics - unit of measurement
Coulomb
Laws of Electrostatics
- Like charges repel, opposite charges attract
- Solid objects - only electrons move
- Solid objects - free electrons only exist on surface
- Solid objects - free electrons concentrate near point of greatest curvature
Electrification
Movement of electrons from one object to another so number of electrons in both objects is unequal
Static electricity is generally caused by electrification by ___
friction
To minimize static, humidity should be above ___
40%
Electrification - Contact
Occurs when potential difference exists between 2 objects touching each other
Electrification - Induction
Charge is induced in another object w/o touching it
Electromotive Force (EMF)
Force created by any electric potential difference
Electromotive force - unit of measurement
Volt
Electrodynamics - Conductors
Electrical current flow in most conditions
Electrodynamics - Semiconductors
Electrical current flow in certain conditions
Electrodynamics - Insulators
No electrical current flow
Electrodynamics - Current
Flow of loosely-bound outer shell electrons
Current - unit of measurement
Ampere / Amp
1 Coulomb per second
1 Coulomb per second is equal to ___
1 ampere
Current flow & electron flow are in ___ directions
opposite
Series circuit
Each component of circuit is connected to each other
Failure of one component breaks the circuit
Parallel circuit
Each component is connected to power source independently
Failure of one component only breaks circuit to that component, not the others
Resistance
Force preventing electrons from moving thru circuit
Resistance affected by:
Length of conductor
Diameter of conductor
Material of conductor
Ohm’s Law
V = I x R
Voltage = Current x Resistance
Electrical power
RATE at which electrical power is used
Electrical power - unit of measurement
Watt (W)
Alternating Current
Oscillation of current back & forth
At frequency of 60 Hertz, each cycle lasts for ___
1/60th second
How many hertz in a second?
60
How many pulses in a hertz?
2
How many pulses in a second?
120
3 ways to generate alternating current
- Move conductor back & forth thru magnetic field - most common
- Move magnetic field back & forth near conductor
- Alternate the strength of magnetic field
Transformer
Use induction to transform voltage & amperage
Step-up transformer
Voltage goes up
Amperage goes down
Step-down transformer
Voltage goes down
Amperage goes up
True/False Induction only works with Alternating Current
True
Autotransformer
Uses concept of self-induction to slightly change voltage in a circuit