Chapter 4 Flashcards
what is Electrostatics?
Stationary electric charges
what is electric charge?
The property of matter
what are electrical charges measured in?
Coulombs
Good _____ have a large # of free electrons.
Conductors
Good _____ have few free electrons.
Insulators
5 General Laws of Electrostatics
1) Like charges repel & unlike charges attract
2) Force between 2 charges is directly proportional to the product of their quantities & inversely proportional to the square of the distance between them
3) reside only on the external surface of conductors
4) Concentration of charges on a curved surface of a conductor is greatest where the curvature is greatest
5) Only negative charges move freely in solid conductors
what is electrification?
when an object gain either a net positive or net negative charge
How can an object be electrified?
By friction, by contact, or by induction
what is electrodynamics?
Electric charges in motion
what must exist for electric current to move?
Electric potential
Define electric potential
Ability to do work due to the separation of charges
Define current
the flow of electrons in a conductor
Define resistance
The property of an element in a circuit that resists or impedes the flow of electricity
what is electric potential measured in?
Volts
What is Current measured in?
Ampere
What is resistance measured in?
Ohm
What is Volts?
The electric potential difference between 2 points
what is ampere?
The amount of current flowing with an electric potential
What is Ohm?
The electrical resistance in a conductor
In what direction does direct current flow?
Flows in one direction
In what direction does alternating current flow in?
Changes direction
Does production of x-rays use alternating or direct current?
Both
what is Ohm law formula?
Voltage = Ampere*Resistance
what are 4 conductor resistors?
1) Material
2) Length
3) Cross-sectional area
4) Temperature
what is a closed circuit?
Closed pathway
what is an open circuit?
Open pathway
What is a series circuit?
Circuit elements are wired along a single conductor
what is Parallel circuit?
Circuit elements “bridge” or branch across a conductor
What does grounding do?
Neutralizes any charged object
What is Magnetism?
Ability to attract iron, cobalt, or nickel
What is Flux?
A magnetic field that consist of line of force in space
What are the 3 laws of magnetism?
1) Every magnet has a north & South Pole
2) Like poles repel, opposite poles attract
3) Attraction or repulsion depends on the strength of the poles and inversely w/ the square distance between them
What is nonmagnetic materials?
Materials not attracted to magnetic fields at all
Ex. Glass, wood, plastic
What is diamagnetic material?
Materials weakly repelled by magnetic fields
Ex. Water, mercury, gold
What is paramagnetic materials?
Materials weakly attracted to magnetic fields
Ex. Platinum, gadolinium, aluminum
What is ferromagnetic material?
Materials strongly attracted to magnetic material
Ex. Iron, cobalt, nickel
Who identified the principle of electromagnetism?
Hans Oersted
What did Hans Oersted discover?
That magnetic fields surrounding a conductor could be intensified by a solenoid
Michael Faraday discovered what?
Moving a conductor through a magnetic field induces an electric current called electromagnetic induction
What is mutual induction?
Induction of electricity in a secondary coil by a moving magnetic field
What is self induction?
Magnetic field created in a coil carrying electrical current
What are electric generators?
Devices that convert some form of mechanical energy
What are electric motors?
Devices that convert electrical energy into mechanical energy through electromagnetic induction
What are transformers?
Devices that increase / decrease voltage through electromagnetic induction
What does a step-up transformer do?
Increase voltage
What does a step-down transformer do?
Decrease voltage
what type of transformer has a ferromagnetic core to maximize efficiency?
Closed core and shell type transformer
what does the Primary circuit consist of?
- main power switch
- circuit breaker
- auto transformer
- timer circuit
- primary side of step-up transformer
what does the Secondary circuit consist of?
- secondary side of step-up transformer
- mA meter
- rectifier bank
- x-ray tube
what does the Filament circuit consist of?
- rheostat
- step-down transformer
- filaments
what is the line compensator?
a device wired to the auto transformer that adjusts power supplied to the x-ray machine to 220 volts
what is the auto transformer?
an adjustable transformer controlled by the kVp selector on the opening console
what is the mA meter?
device that monitors x-ray tube current
what is a rectifier?
device that converts alternating current (AC) to direct current (DC)
what is a half-wave rectification?
half of the AC cycle flows through the x-ray tube and the other half is blocked
what is a single phase?
100% ripple
what is a 3 phase, full wave rectification?
13% to 3.5% ripple
what is high frequency, full wave rectification?
< 1% ripple
what is a rheostat?
a resistor controlled by the mA selector on the operating console
what is an exposure timer?
a device that determines the quality of electrons boiled off the filament
what are filaments?
tiny coils of wire housed in the cathode of the x-ray tube
