D Bushong Flash Cards Ch 5 PDF

The primary function of an x-ray convert electric energy into imaging system is to: electromagnetic energy. Electric energy is supplied to the x-ray imaging systems in the form of well...

The primary function of an x-ray convert electric energy into imaging system is to: electromagnetic energy. Electric energy is supplied to the x-ray imaging systems in the form of well electric current. controlled: A conversion takes place in the x-ray tube, where most of this electric energy heat, some of it into x-rays. is transformed into: Figure 4-2 shows other, more familiar examples of electric energy conversion. electric charge restores the chemical When an automobile battery runs down, energy of the battery. an: Figure 4-2 electric energy is converted into mechanical energy with a device electric motor. known as an: Figure 4-2 a kitchen toaster or electric thermal energy. range converts electric energy into: Electric charge comes in discrete units positive or negative. that are: Electrons and protons are the smallest electric charge. unit of: The electron has one unit of: negative charge. The proton has one unit of: positive charge. The electric charges associated with an  electron and a proton have the same: magnitude but opposite signs. Because of the way atoms are the outermost shell of one atom to constructed, electrons often are free to another atom. travel from: fixed inside the nucleus of an atom and Protons, on the other hand are: are not free to move. Electrostatics is the study of: stationary electric charges. Matter contains mass and energy electric charge. equivalence. matter also may have: Nearly all discussions of electric charge negative electric charges, that associated deal with: with the electron. any object that has too few or too many Electrified: electrons. The outer shell of electrons of some loosely bound and can be removed types of atoms are: easily. the substances from which they were Removal of electrons electrifies: removed and results in static electricity. removed from the hair and deposited on If you run a comb through your hair, the comb. The comb becomes electrified electrons are: with too many negative charges. tiny pieces of paper as though the comb were a magnet. Because of its excess An electrified comb can pick up: electrons, the comb repels some electrons in the paper, causing the closest end of the paper to become  slightly positively charged. This results in a small electrostatic attractive force. abnormally low number of electrons and The hair is also electrified because it has may stand on end because of mutual an: repulsion. One object that is always available to accept electric charges from an earth. electrified object is the: The earth behaves as a huge reservoir stray electric charges. In this capacity, it for: is called an electric ground. During a thunderstorm, wind and cloud another (by induction). Both such clouds movement can remove electrons from become electrified one negatively and one cloud and deposit them on: one positively. discharge can occur between the clouds, in this case, electrons are rapidly If the electrification becomes transported back to the cloud that is sufficiently intense, a: deficient. This phenomenon is called lightning. Lightning can occur between clouds, it an electrified cloud and the earth. most frequently occurs between: the electron. This charge is too small to The smallest unit of electric charge is: be useful, so the fundamental unit of charge is the Coulomb (C). 1C= 6.3x10^18 electron charges. Like charges: repel.  Unlike charges: attract. Associated with each electric charge is electric field. an: outward from a positive charge and The electric field points: toward a negative charge. Uncharged particles do not have: an electric field. The force of attraction between unlike charges or repulsion between like Electrostatic force: charges is attributable to the electric field. The electrostatic force is directly proportional to the product of the Coloumb's Law: electrostatic charges and inversely proportional to the square of the distance between them. F=k QaQb/d2 F = the electrostatic force (newton) Coulomb's Law Equation: Qa,Qb= electrostatic charges (coulomb) d= distance between the charges (meter) k= constant of proportionality are close but decreases rapidly as objects The electrostatic force is very strong separate. This inverse square when objects: relationship for electrostatic force is the same as that for x-ray intensity. Electric charge distribution is: uniform throughout or on the surface. When a diffuse nonconductor such as a the electric charges are distributed rather  thunder cloud becomes electrified: uniformly throughout. With electrified copper wire, excess on the outer surface. electrons are distributed: Electric charge of a conductor is sharpest curvature of the surface. concentrated along the: stored energy. Such a system has the A system that possesses potential energy ability to do work when this energy is is a system with: released. Electric charges have: potential energy. When positioned close to each other, electric potential energy because they like electric charges have: can do work when they fly apart. electric potential because the Electrons bunched up at one end of a electrostatic repulsive force causes some wire create an: electrons to move along the wire so that work can be done. volt (V): the unit of electric potential. The higher the voltage, the greater: the potential to do work. In the US, the electric potential in homes 110 V. and offices is: X-ray imaging systems usually require: 220 V or higher. The volt is potential energy per unit joule/coulomb. (1 V = 1 J/C) charge or:  We recognize electrodynamics electricity. phenomena as: If an electric potential is applied to then electrons move along the wire. This objects such as copper wire: is called electric current, or electricity. Electrodynamics: the study of electric charges. The direction of electric current is opposite that of electron flow. always: Electrical engineers work with electric current, physicists are usually concerned electron flow. with: substance through which electrons flow A conductor is any: easily. most metals, copper is one of the best, and water is also a good conductor Good electrical conductors: because of the salts an other impurities it contains. glass, clay, and other earthlike materials Examples of insulators: are usually good insulators. The principal semiconductor materials silicon (Si) and germanium (Ge). are: under some conditions behaves as an A semiconductor is a material that: insulator and in other conditions behaves as a conductor.  At room temperature, all materials: resist the flow of electricity. Resistance decreases as the temperature reduced. of material is: some materials exhibit no resistance Superconductivity: below a critical temperature (TC). niobium and titanium allow electrons to Superconducting materials such as: flow without resistance. Ohm's law does not pertain to superconductors. perpetual motion because electric A superconducting circuit can be viewed current exists without voltage. It must as one in: be made very cold, which requires energy. Modifying a conducting wire by reducing its diameter (wire gauge) or increase its resistance. inserting different material (circuit elements) can: the resistance is controlled and the Electric circuit: conductor is made into a closed path. a reduced electric current. Increasing electric resistance results in: Electric current is measured in: amperes (A). number of electrons flowing in the The ampere is proportional to the: electric circuit. electric charge of 1 C flowing through a  One ampere is equal to an: conductor each second. Electric potential is measured in: volts (V). Electric resistance is measured in: ohms (Ω). high potential energy and high capacity Electrons at a high voltage have: to do work. If electron flow is inhibited, the circuit high. resistance is: the voltage across the total circuit or any Ohm's law: portion of the circuit is equal to the current times the resistance. V=IR, R=V/I, I=V/R V= the electric potential in volts Ohms law equation: I= the electric current in amperes R= the electric resistance in ohms Usually, electric circuits can be reduced Series circuit or parallel circuit. to one of two basic types: In a series circuit, all circuit elements connected in a line along the same are: conductor. A parallel circuit contains elements that connected at their ends rather than lying are: in a line along a conductor. sum of the individual resistances. The Rules for series circuits, the total current through each circuit element is resistance is equal to the: the same and is equal to the total circuit current. The sum of voltages across each circuit element is equal to the total  circuit voltage. equal to the total circuit current. The voltage across each circuit element is the Rules for parallel circuit, the sum of the same and is equal to the total circuit currents through each circuit element is: voltage. The total resistance is the inverse of the sum of the reciprocals of each individual resistance. Christmas lights are a good example of series and parallel circuits. the difference between: one wire that connects each lamp, when Christmas lights wired in a series have one lamp burns out, the entire string of only: lights goes out. two wires that connect each lamp, when Christmas lights wired in parallel, have: one lamp burns out, the rest remain lit. Electric current, or electricity, is the: flow of electrons through a conductor. electrons can be made to flow in one Direct current (DC): direction along the conductor. Most applications of electricity requires one direction and then in the opposite that electrons be controlled so they flow direction. first in: current in which electrons oscillate back Alternating current (AC): and forth. Figure 4-13 diagrams the phenomenon of DC and shows how it can be graph called a waveform. described by a:  The horizontal axis, or: x-axis, of the current waveform represents time. y-axis represents the amplitude of the The vertical axis, or: electric current. horizontal line. The vertical separation For DC, the electrons always flow in the between this line and the time axis same direction, therefore DC is represents the magnitude of the current represented by a: or voltage. The waveform for AC is a: sine curve. positive direction with increasing Electrons flow first in a: potential and the negative direction. This oscillation in electron direction 1/60 s. occurs sinusoidally with each requiring: 60 Hertz current (50 Hertz in Europe AC is identified as a: and in much of the rest of the world). Electric power is measured in: watts (W). Common household electric appliances such as toasters blenders mixers and 500 to 1500 W of electric power. radios generally require: Light bulbs require: 30 to 150 watts. Of electric power. An x-ray imaging system requires: 20 to 150 kW of electric power. 1 watt is equal to: 1 A of current flowing through an  electric potential of one V. Power= voltage (V) x current (A). an oxide of iron (Fe304). This rod like stone, when suspended by a string, would rotate back and forth, when it Magnetite: came to rest, it pointed the way to water. It was called a lodestone or leading stone. Magnetism is a fundamental property of matter. some forms of: Any charged particle in motion creates magnetic field. a: The magnetic field of a charged particle perpendicular to the motion of that such as an electron in motion is: particle. If the electrons motion is a closed loop, as with an electron circling a nucleus, perpendicular to the plane of motion. magnetic field lines will be: electrons behave as if they rotate on an axis clockwise or counterclockwise. Electron spin: This rotation creates a property called electron spin. magnetic field, which is neutralized in electron pairs. Therefore, atoms that The electron spin create a: have an odd number of electrons in any shell exhibit a very small magnetic field. Spinning electric charges also induce a: magnetic field.  Magnetic moment: the proton in a hydrogen nucleus spins on its axis and create a nuclear magnetic dipole called a magnetic moment. This forms the basis of MRI. The lines of a magnetic field are always: closed loops. The lines of a magnetic field do not start bipolar or dipolar, it always has a north or end as the lines of an electric field do. and a south pole. Such a field is called: the small magnet created by the electron Magnetic dipole: orbit. an accumulation of many atomic Magnetic domain: magnets with their dipoles align creates a magnetic domain. If all the magnetic domains in an object magnet. are aligned, it acts like a: Under normal circumstances, magnetic randomly distributed. domains are: an external magnetic field, such as the earth in the case of naturally occurring When a ferromagnetic material is made ores or an electromagnet in the case of into a permanent magnet: artificially induced magnetism, randomly oriented dipoles align with the magnetic field. The magnetic dipole in a bar magnet can imaginary lines of magnetic field. be thought of as generating: not disturbed. However, if a If a non magnetic material is brought ferromagnetic material such as soft iron near such a magnet, these field lines are: is brought near the magnet, the magnetic field lines deviate and are concentrated into the ferromagnetic material. material to attract the lines of magnetic Magnetic permeability is the ability of a: field intensity. 1) naturally occurring magnets There are three principal types of 2) artificially induced permanent magnets: magnets 3) electromagnets. Magnets are classified according to the magnetic property. origin of the: Artificially produced permanent magnets are available in many sizes and iron. shapes but principally as a bar or horseshoe magnets, usually made of: A prime example of an artificial compass. permanent magnet is A: permanent. One can destroy the magnetic properties of a magnet by heating it or even hitting it with a Permanent magnet do not necessarily hammer. Either act causes individual stay: magnetic domains to be jarred from their alignment. They see us again become randomly aligned, and magnetism is lost. Electromagnet consists of wire wrapped iron core. around an: When an electric current is conducted magnetic field is created. through the wire, a:  The intensity of the magnetic field is current. proportional to the: The iron core greatly increases the: intensity of the magnetic field. All matter can be classified according to magnetic field. the manner in which it interacts with an: magnetic field. Such materials are non Many materials are unaffected when magnetic and includes substances such brought into a: as wood and glass. weakly repelled by either magnetic pole. Diamagnetic materials are: They cannot be artificially magnetized, and they are not attracted to a magnet. Examples of diamagnetic materials are: water and plastic. iron, cobalt, and nickel. These are strongly attracted by a magnet and Ferromagnetic materials include: usually can be permanently magnetized by exposure to a magnetic field. an alloy of aluminum nickel and cobalt Alnico: it is one of the more useful magnets produced from ferromagnetic material. Rare earth ceramics have been stronger magnets. developed recently and are considerably: ferromagnetic and non magnetic. They Paramagnetic materials lie somewhere are very slightly attracted to a magnet between: and are loosely influenced by an external magnetic field. Examples of ferromagnetic materials: contrast agents used in MRI. The degree to which a material can be magnetic susceptibility. magnetized is its: when wood is placed in a strong magnetic field, it does not increase the Low magnetic susceptibility: strength of the field. Wood has low magnetic susceptibility. when iron is placed in a magnetic field, it greatly increases the strength of the High magnetic susceptibility: field, iron has high magnetic susceptibility. The physical laws of magnetism are electrostatics and gravity. similar to those of: 1) magnetism The three forces that are considered 2) electrostatics fundamental: 3) gravity In contrast to the case with electricity, magnetism. there is no smallest unit of: smaller magnets, which when divided Dividing a magnet simply creates two: again and again make baby magnets. How do we know that these imaginary lines of the magnetic field exist? They iron fillings near a magnet. can be demonstrated by the action of: If a magnet is placed on a surface with ends of the magnet. small iron fillings, the fillings attach most strongly and with greater  concentration to the: poles, a North Pole and the South Pole Every magnet has two: analogous to positive and negative electrostatic charges. As with electric charges, like magnetic repel, and unlike magnetic poles attract. poles: The imaginary lines of the magnetic north pole of a magnet and return to the field leave the: south pole. Just as an electrostatic charge can be induced from one material to another, magnetic by induction. some materials can be made: magnetic lines of induction, and the The imaginary magnetic field lines are density of these lines is proportional to called: the intensity of the magnetic field. Ferromagnetic objects can be made into: magnets by induction. When ferromagnetic material, such as a induction are altered by attraction to the piece of soft iron, is brought into the soft iron, and the iron is made vicinity of an intense magnetic field, the temporarily magnetic. lines of: If copper, a diamagnetic material, were no such effect. to replace the soft iron, there would be: magnetic sink by drawing the lines of Ferromagnetic material acts as a: the magnetic field into it. When ferromagnetic material is does not retain its strong magnetic removed from the magnetic field, it property. Soft iron, therefore, makes an  usually: excellent temporary magnet. external field for a long period, however, some ferromagnetic materials If properly tempered by heat or exposed retain their magnetism when removed to an: from the external magnetic field and becomes permanent magnets. The electric and magnetic forces were Maxwell's field theory of joined by: electromagnetic radiation. The force created by a magnetic field similarly. and the force of the electric field behave: product of the magnetic pole strength The magnetic force is proportional to divided by the square of the distance the: between them. The earth behaves as though it has a bar magnet in bedded in it. large: At the equator, the North Pole of a Earth\'s North Pole which is actually the compass seeks the: Earth\'s South Magnetic Pole. As one travels toward the North Pole, Earth, not at the geographic North Pole the attraction of the compass becomes but at a region in northern Canada the more intense until the compass points magnetic pole directly into the: The magnetic pole in the southern Antarctica. There, the north end of the hemisphere is in: compass would point toward the sky. The SI unit of magnetic field strength is tesla. An older unit is the gauss. One the: tesla (T) = 10,000 gauss (G)  The Earth\'s magnetic field is 50 microtesla at the equator and 100 approximately: microtesla at the poles. A magnet on a cabinet door latch is 100 mT. approximately: MRI magnet strength is approximately: 3 T. The development of methods for producing a steady flow of charges (an both electricity and magnetism. electric current) during the 19th century stimulated investigations of: electromagnetic phenomena and These investigations lead to an enhanced ultimately led to the electronic understanding of: revolution on which today's technology is largely based. Luigi Galvani made an accidental two different metals just as if it had been discovery. He observed that a dissected touched by an electrostatic charge. frog leg twitched when touched by: This prompted Alessandro Volta to question whether an electric current metals are brought into contact. might be produced when to different: Using zinc and copper plates, Volta feeble electric current. succeeded in producing a: copper zinc plates like a Dagwood To increase the current, Volta stacked sandwich to form what he called the the: voltaic pile a precursor of the modern battery. Cell of a battery: each zinc-copper sandwich.  carbon rod as the positives electrode surrounded by and electrolytic paste Modern dry cells use a: housed in a negative zinc cylindrical can. The battery is a device that is an electric potential. example of sources of: Any device that converts some form of energy directly into electric energy is electric potential. said to be a source of: Electric potential is measured in units Joule per Coulomb, or volt. of: When scientists finally had a source of a link between electricity and magnetism constant electric current Hans Oersted, in 1820. discovered: Oersted fashioned a long straight wire, supported near a free rotating magnetic pointed north as expected. compass. With no current in the wire, the magnetic compass: When a current passed through the wire, swung to point straight at the wire. however the compass needle: Here we have evidence of a direct link electric and magnetic phenomena. between: magnetic field strong enough to The electric current evidently produced overpower the Earth's magnetic field a: and cause the magnetic compass to point toward the wire.  Any charge in motion induces: magnetic field. no magnetic field. Electrons that flow A charge at rest produces: through a wire produces a magnetic field about that wire. imaginary lines that form concentric The magnetic field is represented by: circles centered on the wire. concentric circles around each tiny Magnetic field lines form: section of a loop of the wire. Because the wire is curved, however, overlap inside the loop. these magnetic field lines: In particular, at the very center of the come together, making the magnetic loop, all of the field lines: field strong. intensity of the magnetic field running Stacking more loops on top of each through the center or axis of the stacked other increases the: loops. The magnetic field of a solenoid is center of the coil. concentrated through the: A coil of wire is called a: solenoid. The magnetic field can be intensified wrapping the coil of wire around further by: ferromagnetic material, such as iron. The iron core intensifies the: magnetic field. An electromagnet is a: current carrying coil of wire wrapped  around an iron core which intensifies the induced magnetic field. A bar magnet and an electromagnet are magnetic field can be adjusted by the same. Of course, the advantage of varying the current through its coil of the electromagnet is that its: wire. electricity can be used to generate Oersted experiment demonstrated that: magnetic fields. It is obvious, then, to wonder whether the reverse is true , can magnetic fields generate electricity. somehow be used to: magnetism can be used to generate Michael Faraday found that: electricity. Faraday discovered that when the moved, the coiled wire does have a magnet is: current, as indicated by the ammeter. an electric current is induced in a circuit Electromagnetic induction: if some part of that circuit is in a changing magnetic field. 1. the strength of the magnetic field 2. the velocity of the magnetic field as it Faraday\'s law, the magnitude of the moves past a conductor induced current depends on four factors: 3. the angle of the conductor to the magnetic field 4. the number of turns in the conductor Actually, no physical motion is needed. increased or decreased its magnetic field An electromagnet can be fixed near a will likewise change and induce a coil of wire. If the current in the current in the coil. electromagnet is then:  A prime example of electromagnetic radio reception. induction is: Radio emission consists of: waves of electromagnetic radiation. Each wave has an oscillating electric electrons in the radio antenna, resulting field and an oscillating magnetic field. in a radio signal. The signal is detected The oscillating magnetic field induces and decoded to produce sound. motion in: Varying magnetic field intensity induces electric current. an: To practical applications of Oersted and electric motors and generators. Faraday\'s experiments: electric current produces a mechanical Electric motor: motion. mechanical motion induces electricity in Electric generator: a coil of wire.