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Rad Physics Test 2

Electromagnetic Energy, Electricity, and Magnetism

Electromagnetic Energy energy continuum around us; we can only see a small segment of this energy (visible light); uninterrupted
Photon atom (quantum) of light; small bundle of energy traveling through space at the speed of light (3 x 10^-8); *smallest type of electromagnetic energy; displays electric and magnetism properties
4 Properties of Electromagnetic Energy frequency, wavelength, amplitude and velocity
Frequency number of wavelengths passing a point of observation per second; rate of rise and fall; hertz = 1 signwave
High vs. Low Frequency high freq- rise and falls are much closer together low freq- rise and falls are more spread out
Wave Amplitude how tall; 1/2 range from crest to valley
High vs. Low Amplitude high amp- hills are much taller low amp- hills are shorter
Wavelength distance between crests of wave; Greek letter lambda λ
Wave Equation wavelength = velocity/frequency λ=c/f c= velocity; speed of light
Indirect or Direct Relationship for c (velocity), f (frequency), and λ (wavelength) c=_f so, directly related c=λ_ so, directly related _= λf so, indirectly related
Electromagnetic Spectrum visible light, x-radiation, and radio-frequency
If increase frequency, what happens to electromagnetic energy? electromagnetic energy increases
Visible Light identified by wavelength; smallest segment of electromagnetic spectrum; very low energy and long wavelength; can be refracted
Radiowaves identified by frequency; very low energy and long wavelength; overlaps with microwave emission, cell phones, etc. AM station = long WL, decrease frequency FM station = short WL, increase frequency
Ionizing Radiation characterized by energy of photon; more energy than visible light or radiofrequency photons - higher freq - shorter wavelength
2 Types of Ionizing Electromagnetic Radiation xrays: originate in electron shells gamma rays: originate in nucleus
Wave Particle Duality both xrays and visible light photons exhibit both types of behavior - visible light behaves more like waves; bend light - xrays behave more like particles; pool table ball hits and goes in different direction
How does electromagnetic energy behave behaves like a particle or like a wave
Attentuation reduction of intensity by the scatter or absorption of xrays as they pass through pt - radiopaque: not through - radiolucent: goes through
Inverse Square Law radiation intensity is inversely related to the square of the distance from the source; beam spreads out 3ft from beam - dog gets hit more 6ft from beam - dog gets hit with less photons bc intensity has decreased
Particle Model use energy to identify diagnostic energy range: 30-150 kVp; *energy of a photon is directly proportional to its frequency E = hf h= plancks constant/ 4.15 x 10^15 cV
Planck's Quantum Theory xrays are created with speed of light and either exist with velocity or do not exist at all E = hf
Law of Conservation of Matter matter cannot be created or destroyed but can be transformed; total quantity of matter/energy available in universe is fixed and never any more or less; E = mc^2 proves this
Electrical Energy is turned into what? into magnetic energy
Electrostatics *study of stationary electric charges - electrons and protons; no neutrons bc they have no charge and are not electrical
Electricification happens due to the movement of negative electric charge (e-); too few or too many electrons so needs to get rid of them; can be created by contact, friction (rubbing balloon), or induction tube sock has too many e- and touches old man to get rid of them
Electric Ground an object readily available to take on electric charges; *Earth is the largest electric ground, it acts like a reservoir for stray electric charges; serves as ground for lightening
What is the smallest unit of electric charge? electron but its too small to mathematically use so use coloumb 1C = 6.3 x 10 ^18
Electrostatic Laws unlike charges attract; like charges repel -electric charge: concentrated along sharpest curvature of surface and has uniform distribution - ES force directly related to product of charges and indirectly related to the distance between them
Electrical Potential Unit VOLT; increase volt, increase EP; electric charges have potential energy
4 Electric States of Matter conductors, insulators, semiconductors and super conductor
Conductors object e- flow easily through; ex- copper, water
Insulators e- do not flow through; ex- dry wood, rubber, glass
Semi Conductor sometimes act like conductor sometimes act like insulator; ex- silicon
Super Conductor only become conductors under extremely low temps; have high resistant of e-; ex- titanium
Electrodynamics study of charges in motion; e- flow one way while current goes the other; get magnetic field around e-
OHMS Law Ω the voltage across the total circuit or any portion of the circuit is equal to the current times the resistance V = IR I = current (amps) R = resistance (Ω)
Electric Circuit current can't flow unless continuous loop; increasing electric resistance results in reduced electric current
Examples of Electric Circuits ***Look up in chart***
Series Curcuit all circuit elements are connected in a line along the same conductor
Rules for Series Curcuit total resistance = sum of individual resistances; current through each circuit element is the same and equal to total circuit current; sum of voltages across each circuit element equals the total circuit voltage
Parallel Circuit contains elements that are connected at their ends rather than lie in a line along a conductor; two can go out but if three go out then it stops circuit
Rules for Parallel Circuit sum of currents through each circuit element = total circuit current; voltage across each circuit element is the same and equal to the total circuit voltage; total resistance is the inverse of the sum of reciprocals of each individual resistance
Direct Current electrons flow in one direction along the conductor; ex- batter or anything that uses one
Alternating Current electrons first flow in one direction, then in the other direction; looks like sign wave with current; ex- generator
Electric Power the rate at which electrical energy is transferred by an electric circuit; measured in watts (W); one watt is equal to 1 A of current flowing through an electric potential of 1 V P = IV V = IR volts; P = power in watts
Magnetism any charged particle in motion creates a magnetic field that will be ⊥; magnetic field lines have continuous loop; e- rotate clockwise or counter clockwise (e- spin) as it circles around nucleus; unit = Tesla (T)
Magnet Classification classified according to origin of the magnetic property; natural - earth; permanent - artificially produced; electromagnets - electric current conducted through wire to create magnetic field
Magnetic Interaction with Matter diamagnetic, ferromagnetic, or paramagnetic
Diamagnetic weakly repelled by either magnetic pole
Ferromagnetic * strongly attracted by a magnet and can become permanently magnetized; iron, cobalt, and nickel
Paramagnetic materials lie between ferromagnetic and nonmagnetic; they are slightly attracted to a magnet and loosely influenced by external magnetic field; MRI contrast agents
Magnetic Susceptability degree to which a material can be magnetized; iron yes, wood no
Magnetic Laws every magnet has two poles: north and south; unlike poles attract, like poles repel; leave the north return to the south no smallest part of a magnet
Magnetic Force is proportional to product of magnetic pole strengths divided by square of distance between them; further they get away not as attracted
What kind of electromagnetic force does a battery produce? produces direct current
Volta vs Gavoni Volta questioned Gavoni's work of frog leg jumping; stacked copper and zinc plates (Voltaic Pile)
Han's Oersted proved charge particle; without a current compass pointed north; when current is introduced into wire, compass points to wire; any charge in motion induces a magnet field
Faraday's Law the magnitude of the induced current depends on four factors: the strength of magnet field, velocity of magnetic field as it moves past the conductor, the angle of the conductor to the magnetic field, and the number of turns in the conductor
Lenz's Law *the direction of induced electric current opposes the action that induces it; Lenz found out which direction the electric current induced it
Lenz's Law - Self Induction *1 coil of wire and alternation current to change magnetic field lines; a constant current induces a constant mag field(direct current)
What happens if the current is not longer direct in self induction? the magnetic field will no longer be constant
What happens if the source voltage increases in self induction? the induced-coil voltage will decrease to oppose it
Lenz's Law - Mutual Induction * need two coils; primary and secondary
Electric Generator mechanical energy turned into electrical energy; coil of wire is placed between two magnets while mechanical energy (hand, steam, water, etc.) turn coil; current is induced due to movement of alternating current
Electric Motor electric energy is turned into mechanical energy; makes fan blades turn and runs the anode
Transformers transforms electric potential and current(voltage) into higher or lower intensity; two coils primary and secondary; when current applied through primary, a current is induced in secondary coil
Transformer Law Formula Vs/Vp = Ns/Np V = voltage; N = number of coil turns; s = secondary side; p = primary side; ex on paper
Turns Ratio step up transformer and step down transformer
Step Up Transformer; what happens to current if turns ratio is >1 ; use Ns/Np; voltage is higher on secondary side than primary; voltage increases, so its an inverse relationship
Step Down Transformer if turns ratio is <1; voltage is lower on secondary side
Transformer Insufficiency resistance, hysteresis (constant change of magnetic fields), and eddy currents (copper pipe ex slow down magnetism); all decrease efficiency of transformer
Types of Transformers closed core, auto transformer, and shell type
Closed Core Transformer laminated layers of iron; reduce in Eddy Currents
Auto transformer Transformers iron core, only ONE winding; self induction
Shell Transformer most common and most efficient; confines magnetic field lines
Faraday found out changing magnetic field would induce/create electric current but didn't know which way field lines went
Created by: ajlindauer