# Shared Flashcard Set

## Details

Physics (Chap 3&4)
Chap 3&4
91
Physics
09/25/2015

Term
 Electrification
Definition
 Process of electron charges being added to or subtracted from an object
Term
 The earth is a zero or ______... basically, it has an infinite number of + and - charges in equal distribtuion, and is considered neutral
Definition
 Ground potential
Term
 5 laws of electrostatics
Definition
 1. Law of repulsion and attraction 2. Inverse square law 3. Distribution 4. Concentration 5. Movement
Term
 Law of repulsion & attraction
Definition
 Attraction; like charges repel, unlike charges attract
Term
 Inverse square law
Definition
 Force between 2 objects is inversely proportional to the square of the distance between them
Term
 Distribution
Definition
 Charges reside on the external surfaces of conductors and equally throughout nonconductors. This happens b/c of the law of like charges (- and - don't attract)
Term
 Concentration
Definition
 The greatest concentration of charge will be on the surface where curvature is sharpest. If enough electrons congregate, they can ionize air or discharge to a point of lower concentration. This is why the x-ray tube has a coiled filament.
Term
 Movement
Definition
 Only negative charges move along solid conductors, b/c the electrons outside the nucleus are easily moved along
Term
 Friction
Definition
 One object is rubbed against another, resulting in electrons traveling from one object to the next. (Just like rubbing a balloon on someone's hair)
Term
 Contact
Definition
 Two objects touch, permitting electrons to move from one to the other. A friction interaction occurs when dragging feet along carpet, distributing electrons over your entire body. When you touch an object with a positive charge, a static discharge occurs, usually resulting in light photon distribution.
Term
 Induction
Definition
 Used in the operation of electronic devices. Process of electrical fields acting on one another without contact.
Term
 Electric current
Definition
 Electrons that are moving in predominantly the same directions. many conditions affect the influence of electric current motion.
Term
 Vacuum
Definition
 A space from which air has been removed. X-rays are produced inside a cavuum in the x-ray tube. This prevents electrons passing from cathode to anode from interacting with air to slow them down.
Term
 Some gasses promote electron flow (from + to -) such as______
Definition
 Neon
Term
 metallic conductors such as ______ ______ are the most common pathways provided for movement of electrical current. When thinking of electrical current, think of a tube filled with balls.
Definition
 Copper wire
Term
 Conductors
Definition
 Are materials that faciitate electron flow.  Examples are metals such as copper and aluminum, which tyoucally have one valence electron.
Term
 Insulators
Definition
 Non-conducting materials; rubber, glass, plastic, white nervous tissue (myelinated), typically have their valence shells full or nearly full.
Term
 Semi-conductors
Definition
 Have the ability to either conduct electricity or insulate under certain conditions; Silicon, germanium
Term
 Electrical circuit
Definition
 Pathway (commonly copper wire) that permits electrons to move in a complete circle from their cource, though resisiting electrical devices and back to the source.
Term
 Sources that can cause current flow include:
Definition
 1. Batteries 2. Generators 3. Solar concerters 4. Atomic reactors
Term
 Batteries
Definition
 Which convert chemical energy to electrical
Term
 Generators
Definition
 Convert mechanical energy to electrical
Term
 Solar converters
Definition
 Convert solar photons to electrical energy
Term
 Atomic reactors
Definition
 Convert nuclear energy to electrical energy
Term
 Current flow
Definition
 Electrons will move from highest concentration to lowest concentration
Term
 Current
Definition
 This of as the quantity of electrons flowing within a given amount of time (we use seconds and milliseconds). Measured in Ampers. We adjust the mA at the console to vary the amount of electronswe boil off at the cathode end of the tube, which will eventualy result in quantity of x-ray photons after interaction with the rotating anode.
Term
 Formula for mAs:
Definition
 mA x time (sec) = mAs
Term
 Force/ strength/ potential difference
Definition
 The difference in number of electrons in excess at one end of the circuit and deficiency at the other end (high concentration to low).   Potential difference describes the force or strength of electron flow; measured in volts
Term
 As current flows along the circuit, __________ decreases as electrons get closer to the side of deficiency
Definition
 Potential difference
Term
 Resistance
Definition
 Amount of opposition to current within the circuit, measured in ohms
Term
 Resistance and length of a conductor are ___________. The longer the wire, the more resisitance it has.
Definition
 Directly proportional
Term
 Resistance and diameter of the conductor are _______ proportional. As the diameter increases, resistance decreases (like water through a garden hose).
Definition
 Inversly
Term
 Heat varies in its relationship with __________.
Definition
 Resistance
Term
 Ohm's law
Definition
 The current along a conductor is proportional to the potential difference (force)
Term
 Ohm's law formula:
Definition
 V = IR    V _______ I    X    R   V = potential difference in Volts (force) I = current in Ampters R = resistance in Ohms
Term
 Series curcuit
Definition
 Sends electrons through carious resistance devices by linking them one after another
Term
 Parallel curcuit
Definition
 Provides each resistor with an individual branch
Term
 Parallel circuits offer less resistance to electrical current if all factors are the same, they are not broken when a single resistor is interrupted (as when a ligh bulb burns out).
Definition
 Christmas lights in series circuits do this. If the lights are on a parallel circuit, all other lights remain on.
Term
 Parellel circuits operate with greater current when all other factors are the same, which can be a disadvantage due to _________. Circuit breakers or fuses are installed which interrupt current when a certain temp is reached. Circuit breakers flip up and can be reset, while fuses melt and are not re-usable.
Definition
 To heat build-up
Term
 Rheostat
Definition
 Can be applied as a resistor which allows manual fluctuation of boltage and amperage (volume knob on stereo). The disadvantage is the heat produced as a byproduct of manipulation, and thye are not very useful in high voltage circuits.
Term
 Watt
Definition
 Total amount of power used in an electric circuit   P ____ I  X  R   P = power in watts I = current/ amperes R = Ohms/ resistance
Term
 Magnetic force
Definition
 Occurs when materials have the ability to attract iron (or ferrous metals). When a charged particle is in motion, a magnetic force field perpendicular to the motion will be created.
Term
 Lines of force, lines of flux, or magnetic fields
Definition
 Forced fields created from magnets.
Term
 When outside a magnet, lines of force flow
Definition
 From N to S
Term
 When inside a magent, lines of force flow
Definition
 From S to N (and never intersect)
Term
 The stronger the magnetic field, the greater number of _____________?
Definition
 Number of lines (or flux density)
Term
 The SI unit for magnetic flux
Definition
 Weber (Wb)
Term
 Units for magnetic flux density are
Definition
 Tesla (T) and the Gauss (G)
Term
 1 T
Definition
 = 10,000 G
Term
 Magnets are classified by what type of production?
Definition
 1. Natural magnet 2. Artificial permanent magnet 3. Electromagnet
Term
 Natural magnet
Definition
 Occur over time when natural iron forms within the earth   (Iodestone)
Term
 Artificial permanent magnet
Definition
 Manufactured from a composition of metals which hold permanent charges   (Alnico- aluminum, nickel, colbolt)
Term
 Electromagnet
Definition
 Temporary magnets produced by moving electric current
Term
 Three pertinent laws of magnetism
Definition
 1. Laws of repulsion & attraction 2. Inverse square law 3. Magnetic poles
Term
 Law of repulsion & attraction
Definition
 Like poles repel, unlike poles attract. Also, lines of force moving in the same direction repel, and moving in opposite directions attract
Term
 Inverse square law
Definition
 Intensity of magnetic force is inversely proportional to the square of the distance between them
Term
 Magnetic poles
Definition
 Every magnet has a north and a south pole. No matter how many times it is divided, it maintains the poles.   (dipole)
Term
 Magnetic induction
Definition
 Can be achieved when a nonmagnetized metal temporarily aligns its poles with nearby lines of force from a magnet. Once that magnet is taken away, the poles slowly return after a period of time to a random magnet
Term
 Classifications of magnetic materials:
Definition
 a. Permeability b. Retentivity 1. Ferromagnetic 2. Paramagnetic 3. Diamagnetic 4. Nonmagnetic
Term
 Permeability
Definition
 The ease at which material can be magnetized
Term
 Retentivity
Definition
 Ability of material to stay magnetized
Term
 Ferromagnetic
Definition
 Ferrous metals which are highly permeable and greatly susceptible to induction   (iron, cobalt, nickel)
Term
 Paramagnetic
Definition
 Low permeability and weak attraction to magnetic fields   (Platinum and aluminum)
Term
 Diamagnetic
Definition
 Weakly repelled by all magnetic fields including noth and south poles   (beryllium, bismuth, lead, water)
Term
 Nonmagnetic
Definition
 Not affected by magnetic fields and cannot be magnetized. These materials are formed by ionic or covalent bonds which eliminates their electrons to move freely along a magnetic force   (wood, glass, rubber, plastic)
Term
 Electromagnetism
Definition
 Electricity and magnetism
Term
 Solenoid
Definition
 Is created when current flows through a coiled wire. The strongest magnetic force will be inside the coil.
Term
 Electromagnet
Definition
 Is made of solenoid with an iron core
Term
 The strength of solenoids and electromagnets is determined by?
Definition
 -The number of loops of wire -the currect strength to the wire -and the permeability of the core
Term
 If electric current is removed from a solenoid or electromagnet, what will happen?
Definition
 All magnetic properties disappear
Term
 Factors influencing effectiveness of solenoids or electromagnets include:
Definition
 1. Diameter of the coil 2. Length 3. Current passing along the coil     *Longer soleniod/electromagnet = stronger
Term
 Mutual induction
Definition
 Occurs when two coilds are placed in proximitity and a varying current supplied to the first coil induces a similar flow in the second coil
Term
 Generator
Definition
 Device that functions to convert mechanical energy to electrical energy. Depending on the type of generator, AC or DC can be produced
Term
 AC, DC
Definition
 AC= alternating current DC= direct current
Term
 Motor
Definition
 A device that is supplied with electrical current to produce mechanical motion
Term
 Transformers
Definition
 Composed of two coils placed near one another (w/o an electrical connection), that operates by mutual induction. The number of turns in the primary coil is different from the number of turns in the secondary coil.
Term
 If there are more coils in the secondary transformer?
Definition
 Step-up transformer
Term
 If there are more coils in the primary, what transformer is it?
Definition
 Step-down transformer
Term
 Transformer law
Definition
 All transformers must operate on AC. Factors effecting efficiency of transformers in x-ray equipment 1. Copper loss 2. Hysterisis loss 3. Eddy current loss
Term
 Copper loss
Definition
 The inherent resistance to current flows found in all conductors that results in heat generation. Large diameter high-voltage wire is used to compensate for this
Term
 Hysterisis loss
Definition
 Occurs as the changing current used with AC reverse magnetic fields back and forth, producing resistance
Term
 Eddy current loss
Definition
 Currents that offpose the magnetic field which is inducing them
Term
 Autotransformers
Definition
 Operate on self induction, primary and secondary coils are wrapped around the same core, and these are used to make specific voltage selections along the coil
Term
 Capacitor
Definition
 Device that can accumulate and store an electrical charge
Term
 Rectification
Definition
 X-ray tubes operate best using direct currents, but the transformers operate on AC. That's where rectifiers come on; AC is changed to pulsating DC
Term
 Thermoinic emission
Definition
 The boiling off of electrons at the cathode end of the tube. With AC, magnetic poles can change, which would cause lots of problems if electrons went toward the cathode rather than the anode
Term
 Unrectified voltage
Definition
 This is AC on the secondary side of high voltage step-up transformer. Only the positive portion of the wave is useful in the x-ray tube, cannot be applied yet
Term
 Half-wave rectification
Definition
 The rectifier does not conduct current during the negative portion of the wave, and current can not be safe to administer to the x-ray tube. The output of half-wave rectification results in a loss or waste of half the power supply, and results in 60 x-ray pulses/sec. These contain two diodes (or rectifiers)
Term
 Full-wave rectification
Definition
 Uses four diodes and reverses the negative wave from AC, making the output voltage to the x-ray tube always positive. This results in 120 pulses per second with all voltage useful.
Term
 All modern x-ray equipment uses full-wave rectification, which results in ?
Definition
 Twice the output
Term
 Most common form of transformer is the?
Definition
 Shell type
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