Radiologic physics Chapter 5 Test 4

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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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