Radiologic physics Chapter 5 Test 4
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Kcraft2384 on July 13, 2011
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84 terms
Terms | Definitions |
|---|---|
 primary function of an xray imaging system | convert electric energy to electromagnetic energy |
| electrostatics | study of stationary or fixed electric charges |
| matter has _______ and _______ equivalence. Matter may also have _______. | mass and energy; electric charge |
| smallest units of electric charge | protons and electrons |
| electrons and protons have the same____ but not the same ______. | magnitude;charge (sign) |
| free to travel from the outermost shell of 1 atom to another atom | electron |
| fixed inside the nucleus of an atom and are not free to move | proton |
| 5 laws of electrostatics | repulsion/attraction law, concentration law, distribution law, inverse square law, movement |
| repulsion/attraction law | like charges repel, unlike charges attract |
| distribution law | charges reside on the external surface of conductors |
| concentration law | greatest distribution of charges on a surface on sharpest/toughest curve |
| 3 ways electrification is created | friction, contact and induction (2 types self and mutual) |
| contact | 2 objects touch, electrons move from one object to another |
| friction | objects rub against one another and electrons travel from one to the other |
| induction | process of electric friction acting on one another with out touching |
| static electricity | removal of electrons electrifies the substances from which they are removed |
| electric charge | 6.3 X 10^`8 C |
| electric field | associated w/ electric charge; points outward from pos charge and toward a neg charge. uncharged particles do not have an electric field |
| electric force | force between unlike charges or repulsion b/t like charges due to electric field |
| coulomb's law | electrostatic force b/t 2 charges is directly proportional to the product of their charges and inversely proportional to the square of the distance b/t them |
| electric charge distribution is ______ throughout or _________. | uniform; on the surface |
| electric charge of a ______is concentrated along the ______of the surface | conductor; sharpest curvature |
| electric potential | energy that cause the electrons to move in a conductor, measured in volts (V) |
| electrodynamics | study of electric charges in motion |
| U.S electric potential in home and offices | 110V |
| xray imaging electric potential | 220V or higher |
| what is the most important method? | induction |
| induction method used in the operation of _________ devices | electronic |
| movement of electrons or electricity results from the traveling of _______ | electrons |
| only ____charges can move along a solid conductor | negative |
| positive charges are fixed in the _____ | nuclues |
| electrons move from ______to ______ concentration | high to low |
| _______charge = object with more electrons | negative |
| ___________charge = object with weaker negative charge or an object with fewer electrons than another object | positive |
| electric current travels from _____to ______poles | pos, neg |
| electric/electron flow travels from ______ to _____poles | neg, pos |
| 3 places where electric current takes place | vaccum (xray tube), neon gas, ionic solutions and metals |
| electric current | measure in amperes (A) electric potential applied to objects such as a copper wire, then electrons move along the wire |
| conductor | allows flow ex. copper wire, aluminum, water |
| insulator | restricts flow ex. rubber, wood, glass |
| semiconductor | allow and restrict flow ex. silicon, germanium |
| superconductivity | allow electrons to flow freely with no resistance below certain temp. works well with very cold liquid ex. noibium and titanium wire used in MRI |
| contact causes _______ of charges | equalization |
| resistance | meaures in Ohms ( ) if electron flow is inhibited, the circuit resistance is high |
| Ohm's law | voltage across the total cicuit or any portion of the circuit is equal to the current times the resistance V= IR |
| resistor | inhibits flow of electrons |
| battery | provides electrical potential |
| capacitor | momentarily stores electric charge |
| ammeter | measures electric current |
| voltmeter | measures electric potential |
| switcht | turns circuit on or off by providing inifinte resistance |
| transformer | increase or decreases voltage by fixed amount (AC only) |
| rheostat | variable resistor |
| diode | allows electrons to flow in only one direction |
| 2 basic types of electric circuits | series, parallel |
| series circuit | all circuit elements are connected in a line along the same conductor |
| parallel circuit | contains elements that are connected at their ends rather than lying in a line during a conductor |
| 2 types of electric current | alternating current (AC) and direct current(DC) |
| direct current (slip ring) | electron that flow in only 1 direction |
| alternating current ( commentating ring) | electron that flow alternately in opposite directions 60Hz/cycle 1 cycle=1/60s single 120 double 240 |
| electric power | measure in watts (W) |
| xray power house hold power light buld | 20-150 kW 500-1500W 30-150W |
| electric power equation | P=IV P=power (W) I=current (A) V=electric potential (V) |
| 3 laws of magnetism | attraction/repulsion, inverse square law, poles |
| any charged particles in motion creates a _____ _______. | magnetic field |
| the lines of a magnetic field are always _____ loops | closed |
| dipole | 2 poles |
| magnetic domain | accumulation of many atomic magnets with their dipoles aligned |
| gauss; tesla | both are units of magnetic intensity 10,000 gauss=tesla |
| 3 principle types of magnets | naturally occuring-earth/lodestone artificial/permanent- iron, nickel, cobalt temporary electromagnet- coiled wire with iron core as induce on wire you get a magnetic field, ceiling fan |
| 4 magnetic states of matter | nonmagnetic-wood, glass diamagnetic-water, plastic paramagnetic- gadolinium ferromagnetic-iron, nickel, cobalt |
| induction | ability to transfer energy from one object to another with out touching. ferromagnetic objects |
| Orsted | electric charges in motion creates a magnetic field |
| Farraday | moving magnetic field near a conductor creates current |
| Farraday's Law's (4) 1st law of electrodynamics | 1. strength of the magnetic field 2. velocity of the magnetic field as it moves past the conductor 3. angle of the conductor to the magnetic field 4. # of turns in the conductor (more turns greater intensity) |
| Lenz | varying magnetic line of force near conductor and create current |
| what is the difference b/t generator and motor | generator - converts mech to electrical motor-converts electrical to mech |
| transformer | transform electric potential and current into high and low intensity. operates on AC, changes amplitude of voltage |
| 3 types of transformers | closed core, autotransformer, shell type |
| closed core | - square core of ferromagnetic |
| autotransformer | iron core transformer with only 1 winding |
| shell type | confined even more the magnetic field lines most efficient for the use of xrays |
| step up transformer | 1,000/1 output is lower than input secondary current is higher than primary greater than 1 |
| step down transformer | 1/1,000 less than 1 |
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