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RADT 334
Radiation Physics- unit 2
| Question | Answer |
|---|---|
| smallest units of electric charge | electrons and protons |
| positive charges do not move | they're trapped inside the nucleus |
| smallest unit of electric charge | electron |
| coulomb (C) | 6.3 x 10^18 electron charges |
| electrostatic laws | unlike charges attract; like charges repel; electric charge of a conductor is concentrated along the sharpest curvature of the surface; electric charge distribution is uniform thru out or on the surface; electrostatic force is directly prop to the product |
| electrodynamics | study of electric charges in motion; conductors, insulators, semiconductors, superconductivity matter |
| V= | IR; I=current (A), R= resistance (ohms) |
| series circuit | all circuit elements are connected in a line along the same conductor |
| rules for series circuit | total resistance is equal to the sum of the individual resistance |
| parallel circuit | elements that are connected at their ends rather than lie in a line along a conductor |
| rules for parallel circuit | sum of the current thru each circuit element is equal to the total circuit voltage |
| direct current | electrons flow in one direction along the conductor; batteries |
| alternating current | first flow in one direction, then in the other direction |
| electric power | measured in watts, P=I^2R; P=power in watts, R=resistance, I=current, V=volts |
| magnetic domain | many accumulations of atomic magnets with dipoles aligned |
| magnetic field strength is measured in | tesla |
| diamagnetic | weakly repelled by either magnetic pole |
| ferromagnetic | strongly attracted by a magnet and can become permanently magnetized; iron, cobalt, and nickel |
| paramagnetic | between ferromagnetic and nonmagnetic, slightly attracted to a magnet and loosely influenced by an external magnetic field; magnetic contrast |
| magnetic laws | every magnet has a north and south pole, unlike poles attract, like poles repel, leave the north, return to the south |
| Oersted | any charge in motion induces a magnetic field |
| selenoid | coil of wire, more intense in center of the wire |
| increase intensity | increase current to coil |
| decrease magnetic | decrease current |
| Faraday's law | strength of the magnetic field, velocity of the magnetic field as it moves past the conductor, angle of the conductor to the magnetic field, number of turns in the conductor |
| Lenz's law | direction of induced electric current opposes the action that induces it, self induction (1 coil), mutual induction (2 coils), primary and secondary |
| electric generator | mechanical energy: turned into electrical energy thru induction |
| electric motor | electric energy is turned into mechanical energy, induction motor takes place in the x-ray tube |
| transformers | transforms electric potential and current into higher or lower intensity; Vs/Vp=Ns/Np, N=number of windings, V=volts |
| step up transformer | turns ratio > than 1; voltage is higher on the secondary side than primary |
| step down transformer | turns ratio < than 1; voltage is lower on the secondary side |
| voltage and current are | inversely proportional |
| types of transformers | closed core, autotransformers, and shell type |
| closed core transformer | laminated layers of iron, reduce Eddy currents |
| autotransformers | iron core, only 1 winding, self induction |
| shell type | most common, operates on mutual winding |
| self induction | 1 coil |
| mutual induction | 2 coils, alternating current in a secondary coil by supplying an alternating current to the primary coil |
| increase intensity | distance decreases |
| increase energy | increase frequency |
| photons | aka quantum, bundle of energy, travels and the speed of light, has electromagnetic properties |
| amplitude | 1/2 range of crest and valley |
| wave equation | wavelength=velocity/frequency |
| c= | lambda*frequency |
| electromagnetic spectrum | radiowaves, microwaves, infrared, visible, UV, x-ray, gamma |
| visible light | identified by wavelengths, smallest segment of electromagnetic spectrum, very low energy and long wavelength |
| what parts of the electromagnetic spectrum used in x-rays | x-rays, visible light, and radiowaves (in MRI) |
| radiowaves | identified by frequency, very low energy, long wavelength |
| ionizing radiation | characterized by the energy of the photon, 2 types x-rays and gamma |
| difference between x-rays and gamma rays | origin |
| visible light tends to behave more like | waves than particles |
| x-rays tend to behave more like | particles than waves |
| transparent | light is transmitted unaltered |
| translucent | light is transmitted but scattered and is reduced in intensity |
| opaque | light is totally absorbed |
| attenuation | reduction in intensity by the scatter or absorption of x-rays as they pass through matter |
| inverse square law | radiation intensity is inversely related to the square of the distance from the source |
| diagnostic energy range is | 30-150 kV |
| E= | hf |
| law of conservation of matter | matter cannot be created or destroyed but can be transformed |
| law of conservation of energy | states that energy cannot be created or destroyed, but can change its form |
| example of conductor | copper and aluminum |
| example of insulator | rubber and glass |
| example of superconductivity | niobium and titanium |
| velocity of all electromagnetic radiation is | 3 x 10^8 m/s |
| diagnostic ultrasound is | not part of the electromagnetic spectrum |
| the energy of a photon is | directly proportional to its frequency |
| only difference between x-rays and gamma rays is | origin |
| electrification | created by contact, friction, or induction |
| coulomb's law | electromagnetic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance between them |
| example of semiconductor | silicone and germanium |
| resistors function | inhibits flow of electrons |
| batteries function | provides electric potential |
| capacitors function | momentarily stores electric charge |
| transformers function | increases or decreases voltage by fixed amount (only AC) |
| diodes function | allows electrons to flow in only one direction |
| Ohm's law | voltage across the total circuit or any portion of the circuit is equal to the current times the resistance |
| one watt is equal to | 1 A of current flowing thru an electric potential of 1 V. |
| W=VA or | P=I^2R |
| magnetic susceptibility | degree to which a material can be magnetized |
| nonmagnetic materials | wood or glass |
| diamagnetic materials | water or plastic |
| paramagnetic material | gadolinium |
| ferromagnetic materials | iron, nickel, or cobalt |
| ferromagnetic objects can be made into | magnets by induction |
| si unit of magnet field strength is the | tesla or gauss (1 tesla= 10,000 gauss) |
| electric potential is measured in | units of joules per coulomb or volt |
| radiowaves have very | long wavelengths compared to x-rays |
| refraction | deviation of course that occurs when photons of visible light traveling in straight lines pass from one transparent medium to another |
| electromagnet | coil or wire wrapped around an iron core that intensifies the magnetic field |
| electron spin | momentum of a particle of an atom in a fixed pattern |
| 4 properties of electromagnetic energy | frequency, wavelength, velocity, and amplitude |
| what 2 types of invisible light come from the sun | infrared and UV |
| narrow region in the middle of the electromagnetic spectrum extending from approximately 400 nm (blue) to 700 nm (red) | visible light |
| light consists of photons with wavelengths longer than those of visible light but shorter than those of micro waves | infrared light |
| light from the sun is responsible for molecular interactions that can result in sunburn | UV |
| emission have low energy and relatively long wavelength. They are usually identified by there frequency by communication broadcasters | radiofrequency Emissions |
| very short wavelength radiofrequency emissions | microwave emission |
| what emission has the most energy? x-ray, visible light, or an RF photon | x-ray |
| Some regions in the EMS behave like waves and some behave like particles in their interaction with matter. What is this phenomenon called | wave-particle duality |
| unit of measure is use for radiofrequency | Hertz |
| unit of measure is used for visible light | meters |
| unit of measure for x-radiation | electron volts |
| smallest units of electrical charge | electrons and protons |
| what happens to an object when it has two few or to many electrons? | it becomes electrified |
| electric current measured in | amperes |
| electric resistance measured in | ohms |
| formula for ohm's law | V=IR |
| creates a magnetic field | any charged particle in motion |
| electron spin creates | magnetic field |
| magnet classification | the origin of the magnetic property |
| matter can be classified by | the manner it reacts with an external magnetic field |
| any charge induces | a magnetic field |
| to intensify the magnetic field using a solenoid | wrap the solenoid around a ferromagnetic material |
| advantages of using an electro magnet compared to a a bar magent | magnetic field can be adjusted by varying the current through its coil of wire |
| Oersted's experiment with a current running thought a copper wire that effects a compass is the bases for | electric motor |
| Faraday's experiments with the motion of a magnet near a coild wire is the principle of | electric generator |
| considering electromechanical devices, what equipment, through electric current, produces mechanical motion | electric motor |
| considering electromechanical devices, what equipment, through mechanical motion, induces electricity thought a coil of wire | electric generator |
| motor used in an x-ray tube | induction motor |
Created by:
meechthebeech91
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