# 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)

electron

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

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

110V

220V or higher

induction

electronic

electrons

negative

nuclues

high to low

negative

positive

pos, neg

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

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

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)

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

magnetic field

closed

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
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

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

Example: