- static electricity generally caused by electrification by friction - to minimize static humidity should be above 40%

Physics Final Flashcards by Claudia Sams

Magnetic Moment

The orientation of the magnetic field for a single electron or proton

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Velocity

How fast the energy of the wave moves from one point to another

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Magnetic Domain

A group of atoms that all have their magnetic dipoles pointed in the same direction

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Magnetic fields are strongest…

Near the poles

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Magnetic Dipole

The small magnetic field around an entire atom

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Resonance

The tendency of electromagnetic radiation to interact with substances that have a natural frequency similar to theirs

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Amplitude

The max displacement of media from its equilibrium; strength of the wave, but not the energy

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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

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alternating current

oscillation of current back-and-forth
- At a frequency of 60 Hz each cycle last 1/60th second

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friction

static electricity generally caused by electrification by friction
to minimize static humidity should be above 40%

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nonmagnetic

all other materials that are unaffected by magnetic fields (wood, rubber)

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diamagnetic

Materials that lightly repel a magnetic field (glass, water)

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relationship between frequency and wavelength

and inversely proportional relationship
* frequency, increases wave length must decrease if velocity is constant

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frequency

The number of cycles that pass a fixed point in a second
- Measured in hertz

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electrical power

The rate at which electrical power is used
- Unit: watt

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V=f~

velocity = frequency x wave length

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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