Physics Final Flashcards
Magnetic Moment
The orientation of the magnetic field for a single electron or proton
Velocity
How fast the energy of the wave moves from one point to another
Magnetic Domain
A group of atoms that all have their magnetic dipoles pointed in the same direction
Magnetic fields are strongest…
Near the poles
Magnetic Dipole
The small magnetic field around an entire atom
Resonance
The tendency of electromagnetic radiation to interact with substances that have a natural frequency similar to theirs
Amplitude
The max displacement of media from its equilibrium; strength of the wave, but not the energy
The electromagnetic wave formula
- All electromagnetic waves travel at the speed of light
- If frequency goes up, wave length goes down
- Energy is directly proportional to frequency
alternating current
oscillation of current back-and-forth
- At a frequency of 60 Hz each cycle last 1/60th second
friction
- static electricity generally caused by electrification by friction
- to minimize static humidity should be above 40%
nonmagnetic
all other materials that are unaffected by magnetic fields (wood, rubber)
diamagnetic
Materials that lightly repel a magnetic field (glass, water)
relationship between frequency and wavelength
and inversely proportional relationship
* frequency, increases wave length must decrease if velocity is constant
frequency
The number of cycles that pass a fixed point in a second
- Measured in hertz
electrical power
The rate at which electrical power is used
- Unit: watt
V=f~
velocity = frequency x wave length
induction only works with…
alternating current
x-rays have what kind of nature?
dual nature
- They have qualities of both light photons and physical particles
electrification by induction
A charge is induced in another object without touching it
parallel circuit
each component is connected to the power source independently
- A failure of one component only breaks the circuit to that component, not the others
series circuit
each component of the circuit is connected to each other
- A failure of one component breaks the circuit
Transformers use induction to transform…
- voltage
- amperage
ohms law
V = IR
V
I R
The strength of the attraction/repulsion of polls follows…
The inverse square law
3 ways to generate alternating current
1) move a conductor back and forth through a magnetic field
2) move a magnetic field back and forth near a conductor
3) alternate the strength of a magnetic field
magnetic fields units of measurement
Gauss (G) - roughly the strength of earths magnetic field at the poles
Tesla (T) - equal to 10,000 Gauss
* typical strength of a medical MRI machine is 2T
Coulomb
unit of electrical charge
electrical current can only flow through certain materials…
conductors: electrical current flows in most conditions
Semiconductors: electrical current flows in certain conditions - temp, light, etc.
Insulators: no electrical current flow
attenuation
- The partial absorption of light or x-rays
Radiopaque: allowing very few x-rays to pass
Radiolucent: x-rays can pass easily
hi energies behave like…
particles
light vs. x-rays
reflection: light – yes; x-rays - no
Refraction: light – yes; x-rays – no
Dispersion: light – yes; x-rays – no
Absorption: yes (x-rays with low energy, x-rays, that interact with radiopaque objects)
transmission: yes (x-rays with high energy, x-rays, that do not interact with radiopaque objects)
laws of electrostatics
- like charges, repel, opposite charges attract
- In solid objects only electrons move, free electrons only exist on the surface, free electrons concentrate near the point of greatest curvature
electromagnetism
all moving electric charges develop magnetic fields
paramagnetic
Materials that are only slightly attracted to magnetic fields
current
The flow of loosely bound, outershell electrons
- Unit: the amp
auto transformer
uses the concept of self induction to slightly change the voltage in a circuit
electromotive force
The force created by any electric potential difference
- Unit: volt
electrification by contact
occurs when a potential difference exists between two objects that touch each other
wavelength
The distance between two like points on a wave (crest to crest)
- This constitutes 1 cycle
- measured in Angstroms
* x-ray: .1 - .5 A
Ferromagnetic
Materials that allow their magnetic domains to be easily lined up in the same direction when subjected to a strong external magnetic field
Resistance
How much force is preventing the electron from moving through a circuit
Affected by:
- Length of conductor
- Diameter of conductor
- Conducting material
Retentivity
The ability of a magnet to hold on to its magnetism over time
