Physics xray circuit

the study of stationary electric charges (static electricity)

Electrostatics

What are electrical charges measured in

coulombs

one coulomb is equal to the electrical charge of

6.25×10^8 electrons

water, copper, and gold have

large number of electrons free to move about making them good conductors of electricity

a medium that allows electrons to move

conductor

glass rubber and plastic have

few number of electrons making them good insulators

a material that resists the flow of electrons

insulator

5 general laws of electrostatics

1. like charges repel and unlike attract

2. coulomb’s law

3. electric charges reside only on the external surface of conductors

4. the concentration of charges on a curved surface of a conductor is greatest where the curvature is greatest

5. only negative charges are free to move in solid conductors

the electrostatic force between 2 charges is directly proportional to the product of their quantities and inversely proportional to the square of the distance between them

coulombs law

rubbing a rubber rod with fur

friction

occurs when a metallic object (without charge) is brought into the electric field of a charges object

The results is that some of the electrons in the uncharged object move, creating electricity

electrification by induction

only occurs when the objects are not in contact with each other but close enough for the uncharged object to be the charged object’s electrical field

induction of electricity

the study of electric charges in motion: what we think of as electricity

electrodynamics

for electric current to move, an electric potential must,…

exit

also known as voltage or potential difference

electric potential

to make electrons flow along a conductor there must be

an electrical potential

ability to do work because of a separation of charges; electrons will flow from abundance to deficiency

electric potential

voltage always flows from a

negative potential to positive potential

if one has an abundance of electrons at one end of a wire and an abundance of positive charges at the other end, electrons will what

flow from abundance to deficiency

ability to do work due to a separation of charges

measured in…

electric potential

Volt

an expression of the flow of electrons in a conductor

measured in…

current

ampere

the property of an element in a circuit that resists or impedes the flow of electricity

measured in…

resistance

Ohm

potential difference that will maintain a current of 1 ampere in a circuit with a resistance of 1 ohm

a volt

the expression of the difference in electric potential between 2 points

volt

Kvp

kilovolt peak

equal to the amount of work, that can be done per unit of charge (W=fd, Work=force x Distance)

volt

the ratio of joules to coulombs (volt=joules/coulombs)

a volt

1 coulomb flowing by a given point in 1 second

ampere

flows only in one direction

Ex; batteries

direct current

changes direction in cycles as the electrical potential of the source changes

ex; transformers

alternating current

the electricity that flows in homes in the United states alternates at 60 cycles per second expressed as a frequency of 60 hertz

alternating current

constantly changing direction in the conductor

alternating current

the electrical resistance equal to the resistance between 2 points along a conductor that produces a current of 1 ampere when a potential difference of 1 colt is applied

ohm

the relationship between current and resistance

ohm’s law

V=IR

volts=amps (current) x ohms (resistance)

Amperes to millamperes

move decimal point 3 places to the right

volts to kilovolts

move decimal point 3 places to the left

__________ is directly proportional to the length of the conductor

resistance

a long conductor as more _____ than a short one

resistance

Twisting does not affect ______ as long as the length does not change

resistance

A conductor with a ___________ has a lower resistance than one with a ______________ because of greater external surface area on which electrons can travel

large cross sectional area

small cross sectional area

with metallic conductors the resistance becomes greater as the _______ f the conductor rises

temperature

Materials with an abundance of free electrons that allow a relatively free flow of electricity

conductors

a closed pathway composed of wires and circuit elements through which electricity may flow

electric circuit

pathway over which electrons flow

circuit

a complete pathway for electricity is required for electricity to flow- allowing the flow of electrons- light on

closed circuit

a broken pathway such as when a switch is turned off- light off

open circuit

produced electrons through a chemical reaction, stores an electric charge long term, and provides an electric potential

battery

temporarily stores an electric charge

capacitor

a one way valve device allows electrons to flow in only one direction

diode

a device that can increase or decrease by a predetermined amount

transformer

a protective measure that neutralizes charged objects

grounding

ability of a material to attract iron, cobalt, or nickel

magnetism

Magnetic field consists of lines of force in space

flux

Lines of flux travel from ____ to ___ inside the magnet and _____ to ______ outside the magnet

south pole to north

north pole to south

like poles ______ and opposite poles _____

repel

attract

the strength of the magnetic field is measured in the SI unit….

Tesla T

Glass, wood, and plastic are

nonmagnetic not attracted to magnetic fields at all

water, mercury, gold are

diamagnetic weakly repelled by magnetic fields

iron, cobalt, nickel

ferromagnetic strongly attracted to magnetic materials

first identified the principle of electromagnetism

hans oersted

discovered that electricity flowing through a wire produced a magnetic field

hans oersted

later, it was discovered that the magnetic field surrounding a conductor could be intensified by….

fashioning it into a coil called a solenoid

the magnetic field surrounding a conductor could be intensified FURTHER by….

adding an iron core to the coil called an electromagnetic

less voltage is induced when there are…

fewer coils in the wire

more voltage is induced with a ……

stronger magnetic field strength

less voltage is induced when the speed at which the coil passes through the magnetic field is…

reduced

found that moving a conductor through a magnetic field induces an electric current in that conductor called electromagnetic induction

michael faraday

slowing down the speed at which the conductor passes through the magnetic field results in

reduced electromagnetic induction

the induction of electricity in a secondary coil by a moving magnetic field

mutual induction

mutual induction requires_________to be flowing in the primary coil of wire

alternating curren

induced in the secondary coil during mutual induction

alternating current

states that an induced current flows in a direction that opposes the action (the charging magnetic field) that induced it

Lenz’s law

with _____ induction the secondary current is in the original coil and opposes the original current

self

devices that convert some form of mechanical energy into electrical energy

electric generators

devices that convert electrical energy to mechanical energy through electromagnetic induction

electric motors

moving a conductor through a magnetic field induces an electric current in that conductor

electromagnetic induction

increases voltage and decreases current

step up transformer

decreases voltage and increases current

step down transformer

the change in voltage and current is an ______ relationship

inverse

what transformers have a ferromagnetic core to maximize efficiency

closed core and shell type

what transformer has less power loss because it is closed providing a continuous path for magnetic flux

closed core

what transformer has 2 closed cores so it is the most efficient and commonly used transformers

it has 2 coils of wire primary and secondary

shell type

found in the primary circuit and operates on the principle of self induction

autotransformer

main power switch, circuit breakers, autotransformer, timer circuit, and primary side of step up transformer

primary circuit

secondary side of step up transformer, mA meter, rectifer bank, xray tube

secondary circuit

rheostat, step down transformer, and filaments

filament circuit

an on-off switch for the unit connected to the facility’s power supply

Main power switch

a device usually wired to the autotransformer that automatically adjusts the power supplied to the x-ray machine to 220 volts

line compensator

an adjustable transformer controlled by the kilovolt peak (kVp) selector on the operating console and is where we find the major and minor kVp selectors

autotransformer

measures the incoming voltage to detect a surge or drop

line voltage meter

monitors and measures the voltage induced in the secondary side of the step-up transformer and operates on the motor principle

kVp meter

Closes the circuit between the autotransformer and the step-up transformer and allows electromagnetic induction to occur in the secondary side of he step-up transformer

Exposure switch

located between the secondary side of the autotransformer

and the primary side of the step-up transformer

• Considered a “dead man” switch because it is only closed

when pressure is applied

Exposure switch

used to increase the voltage from the autotransformer to the kilovoltage necessary for x-ray production

step up transformer

where is the Automatic exposure control (AEC) device:

primary circuit

placed between the patient and image receptor to measure the radiation exiting the

patient.

AEC ionization chamber

With all factors set appropriately, the length of exposure

will be based on the

density of the anatomy covering the

detector.

AEC controls only the _____ of radiation reaching the

image receptor and has no effect on other image

quantity

a device placed in the secondary circuit that monitors x-ray tube current

mA meter