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84 terms

Radiologic physics Chapter 5 Test 4

primary function of an xray imaging system
convert electric energy to electromagnetic energy
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
fixed inside the nucleus of an atom and are not free to move
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)
2 objects touch, electrons move from one object to another
objects rub against one another and electrons travel from one to the other
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)
study of electric charges in motion
U.S electric potential in home and offices
xray imaging electric potential
220V or higher
what is the most important method?
induction method used in the operation of _________ devices
movement of electrons or electricity results from the traveling of _______
only ____charges can move along a solid conductor
positive charges are fixed in the _____
electrons move from ______to ______ concentration
high to low
_______charge = object with more electrons
___________charge = object with weaker negative charge or an object with fewer electrons than another object
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
allows flow ex. copper wire, aluminum, water
restricts flow ex. rubber, wood, glass
allow and restrict flow ex. silicon, germanium
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
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
inhibits flow of electrons
provides electrical potential
momentarily stores electric charge
measures electric current
measures electric potential
turns circuit on or off by providing inifinte resistance
increase or decreases voltage by fixed amount (AC only)
variable resistor
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
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
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
ability to transfer energy from one object to another with out touching. ferromagnetic objects
electric charges in motion creates a magnetic field
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)
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
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
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
output is lower than input
secondary current is higher than primary
greater than 1
step down transformer
1/1,000 less than 1