chapters 1-5

Parallel Circuit

• Component parts connected as branches of main circuits

• More resistors added= amperage increases=overloaded circuit

Series circuits

Electric circuit whose components parts are arranged end to end

US today uses ____

• AC at 60Hz- 60 cycles per second

• Flow changes direction 120/sec

Temperature

• directly related to resistance

• Increased atomic motion due too increased temp prevents electrons from flowing freely

Diameter

• inversely related to resistance

• Solid conductor increases, resistance decreases

• Lower #=thicker wire

Length

• directly related to resistance

• Length of solid conductor increase, resistance decreases

Material conductivity

• Conductors: permit flow of e- (metals)

• Insulators: inhibits flow of e- (glass,rubber,wood)

• Superconductors : permit flow of e- with no resistance at certain temps (aluminum)

• semiconductors: permit of e- under certain conditions

Resistance depends on 4 things

1. Material conductivity

2. Length

3. Diameter

4. Temperature

Electrical circuit

Pathway through which electrons move

Atomic reactor

Nuclear > electrical

Solar converter

Solar > electrical

Generator

Mechanical > electrical

Batteries

Chemical > electrical

Electric current

Electrons move from areas with high e- concentration to low e- concentration

In a metallic conductor…

An electric current in a solid conductor consists of a flow electrons only (copper/silver wire)

In a ionic solution…

Electrodes immersed in some solutions attract opposite charged ions, ions moves towards electrodes

In a vacuum…

Electrons jump gap between oppositely charged electrons (X-ray)

In a gas…

Positive and negative ions drift towards opposite charged electrodes in a gas (neon)

Conditions of electrodynamics

• in a vacuum

• In a gas

• In a ionic solution

• In a metallic conductor

Definition of electrodynamics

Electric charges in motion

Movement

Only negative charges move along solid conductors

Concentration

Greatest concentration of charges will gather at sharpest area of curvature

Distribution

Charges reside on external surface of a solid conductor

Repulsion-attraction

• electric field surrounds every charged body

• Like charges repel

• Unlike charges attract

Laws of electrostatics

• repulsion-attraction

• Distribution

• Movement

• Inverse square law

• Concentration

Induction

Bringing a charged body in close proximity to a neutral object w/o physical contact creates a charge in neutral object

Contact

Physically touching a charged body to a neutral body creates a transfer of charge

Friction

Abrasion of 2 conductive materials creates a transfer of charges between the materials

Electrification

Process of adding or removing electrons

Electrostatics

Electric charges at rest, the study of distribution of charges and behavior of charged particles helps us to understand electricity and electrical components

Unit that potential difference is measured in

Volts (V)

Conventional vs. electron flow

• conventional: flow of electrical current form positive to negative terminal of power source

• Electron flow: flow from negative to positive terminal of power source

Inverse square law

Describes how the intensity of a physical quantity decreases as the distance of its source increases

1 ampere

6.24 × 10^18 per second

Power loss formula

P= I² R

Power = current ² x resistance

Electrical power formula

P=IV

power= current x potential difference

Ohms Law formula

V=IR

Potential difference = current x resistance

Dry cell batteries create __

DC

AC vs. DC

• AC: constantly changes direction

• DC: Flows only in one direction

Convert amperes to milliamperes

1A= 100mA

Multiply current value by 1000

Converts volts to kilovolts

1V= 0.001 kV

Divide potential value by 1000

Resistor circuit

Inhibits electron flow

Battery circuit

Provides electrical potential

Capacitor circuit

Momentarily stores electric charge

Ammeter circuit

Measures electric current

Voltmeter circuit

Measures electric potential

Switch circuit

Turns on/off by infinite resistance

Transformer circuit

Increased or decreased voltage by fixed amount (AC only)

Rheostat circuit

Variable resistor

Diode circuit

Electrons flow in only 1 direction

Pulse echo, echo range, and Huygens are the ____ ____

3 Principles of ultrasound image creation

Sound transmitted by ultrasound transducer, into a medium and the sound is reflected back to transducer to create an image

Pulse echo principle

Each echo is placed on the ultrasound image by determining the exact location where the echo came from

Echo range principle

how fast the sound waves is traveling through a medium

How long it takes for the echo to return

finding location of echo

Calculates the length of time it takes for the echo to return

Computer w/ the ultrasound machine

Allows ______ of the _____ between ______ on an ultrasound image

Representation, distance, structures

Ultrasound equipment is _____ for the average _______ of soft tissue

Calibrated, propagation speed

_____ = Short time

Shallow

_____ = long time

Deep

Sound beam is not uniform in shape as it travels (beam width changes)

Huygens principle

Starting point > ______ = transducer diameter

Beam width

½ original value at the transducer/focal zone

Narrowest point

Near field

Transition/focal zone

Focus/focal point

Far field (Fraunhofer zone)

Anatomy of a soundbeam

The ___ ___ is the Region from transducer to focal zone

Near field

Useful beam is equal to about ___ near field lengths

2

Transducer size and operating frequency

Near field is determined by:

The _____ is the Region around focus where the beam is relatively narrow

Transition/focal zone

the ____ is the point of maximum intensity of the sound beam

Transition/focal zone

Reflection arising from the ____ ___ are MORE ____ then those from other depths

Focal zone, accurate

CAN be changed by sonographer

Transition/focal zone

½ of _____ is located in near field, ½ of _____ is located in far field

Focal zone

Location where the beam is narrowest

Focus (focal point)

The width of the sound beam at the focus is ½ the width of the beam as it leaves transducer

disc shaped crystals…

Region starts at the focus and extends deeper

Far field

The area beyond the far field is of no value in forming an image as the b3am becomes too weak

Far field (Fraunhofer zone)

Never stops, endless cycle

Continuous waves

Continuous waves have __ crystals

2

1 emits the pulse

1 listens for returning echo

2 crystals of continuous waves

Continuous and pulsed waves

2 types of sound waves utilized by ultrasounds

Sound waves never stop being emitted by ______

Transducer

Continuous waves emits more _____ then pulsed wave ultrasounds

Power

_____ and _____ remain constant

Amplitude and frequency

Continuous waves are ____

Used in physical therapy

Heat produced helps with ___

Tissue healing

Short burst of acoustic energy that are used to create an atomic images

Has a beginning and a end

Pulsed wave

Pulsed waves are used by ____

Diagnostic ultrasound machines

Pulsed waves have _ crystal

1

Single crystal switches between emitting a pulse and listening for returning echo

Pulsed wave crystal

1

Pulsed wave example

2

Wavelength

3

Amplitude

4

Distance

1

Continuous wave example

pressure

Density

particle vibration

Temperature

Variables of sound waves

particles in the medium as a sound wave passes through

Affects of sound wave variables

____ = force/area

Pressure

Concentration of force over a given area

Pressure definition

Pressure is an ____ ___

Outside force

Particles forced together and pressure increases

During compression…

Pressure decreases and particles resume their normal positron and density

During rarefraction…