chapter 4- Electromagnetism Flashcards
like charges repel
opposites attract
north pole and south pole
magnets
o Force between two magnetic fields directly proportional to product
of their magnitudes and inversely proportional to square of
distance between them
Inverse Square Law
magnets demonstrate :
polarity
inverse square law applies to :
-magnetism
-electric field
-gravity
A coiled, helix of wire carrying
an electrical current
Solenoid
required components for electromagnetic induction
Requires an interaction between a conductor and a magnetic field
o Magnetic field
o Conductor
o Relative motion
Two types of induction
-mutual induction
-self induction
-two coils
-varying current supplied to primary coil
-induces current in secondary coil
-two coils are electrically insulated from each-other
mutual induction
which induction requires step up and step down
mutual induction
which induction is primary to secondary
mutual
where is step down located
in the filament
what happens to the amps when volts is increased
amps decreases
what happens to voltage when mA is increased
voltage decreases
always present in coils supplied with alternating current
self induction
convert mechanical energy to electrical energy
generators
can produce direct current or alternating current
generators
components of generator
armature
magnets
slip rings
brushes
autotransformer and alternating current is your:
self induction
is alternating current rectified or uncertified
unrectified
full wave
is direct current rectified or unrecitified
rectified
1/2 wave
what is your source orgin for voltage
autotransformer
helps deliver current
step down
what design does the direct current generators use
a commutor ring design
what design does the alternating current generators use
slip rings
what circuit do you add all the numbers
series
what circuit do you take the lowest number and cut it in half
parallel
when 1 thing isnt working, the whole thing is down
series circuit
when 1 thing isnt working, just that area/ part isnt working
parallel circuit
olms law
V=IR
v=voltage
I=current
R=resistance
what is your unit for current
amperage
where is your step up and step down
step up - primary to secondary
step down - filament
what happens to your voltage when your amps is increased in step down
Voltage decreases
where is your rectifier located
secondary
is step down your current or voltage
current
what is volts changed to in step up
volts to kilovolts
line voltage compensator
adjusts low/high voltage
what current is rectified and unrectified
AC- unrectified
DC- rectified
xray tube energy is converted to:
mechanical to electrical
- Most efficient type of electrical generation
- Employs an armature with three coils
- 120° apart
- Each phase of induced current is separated by 120°
Three phase generation
- Convert electrical to mechanical energy
- Similar components to generators
- Armature supplied with current
uses Fleming’s Left-Hand Motor Rule
Motors
Synchronous
Coils turn at same rate as
armature supplying
current
Asynchronous
Variable speed
what are the motor types
synchronous and asynchronus
what waves are least efficient to most efficient
-half wave
-full wave
-3phase, 6 pulse
-3phase, 12 pulse
- high frequency
what are the types of meters
ammeter
voltmeter
what meter:
Connected in series
Measures current flow
ammeter
what meter :
Connected in parallel
Measure potential difference between two points in circuit
what controls electrical current
- Transformers
- Autotransformers
- Capacitors
what wave has 1% loss
high frequency
how much loss is in 3 phase 12 pulse
4 percent
how much loss is in 3 phase 6 pulse
13 percent
how much loss is in half and full wave
100 percent
what wave is the third efficient
3 phase 6 pulse
motor components
-rotor
-stator windings
what happens to the voltage and amps in step up and step down
step up:
increase in volts, decrease in amps
Step down:
decrease in volts, increase in amps
electrical storage energy
capacitor
is voltage higher or lower in step up
higher voltage
is voltage higher or lower in step down
voltage is lower
voltage induced in secondary coil directly related to number of turns in secondary coil
transformer law
what is the relationship between voltage and amperage in transformer law
Induced voltage and amperage are inversely proportional
what is the most common and most efficient transformer type
shell type
transformer types
Air Core
Open Core
Closed Core
Shell type
what side is the low and high voltage at
low voltage- primary side
high voltage - secondary side
boiling off electrons
thermionic emission
need for rectification:
xray tube can only operate on direct current
process of alernating to direct current
rectifier
-full wave more efficient
two designs for autotransformer
o Primary and secondary coils connected in series
o Single coil on central core
three divisions for basic xray circuit
- Low voltage circuit
- High tension circuit
- Filament circuit
- Accumulates and stores electrical charge
- Charged with DC voltage
- Unit of capacitance
capacitors
- Process of changing AC to DC
Rectification
- Primitive form of current rectification
- Performed by x-ray tube which acts as a diode device in the
circuit - X-ray tube not designed to be a diode rectifier
- Produces a DC waveform that is 50% of full-wave rectification
- Very inefficient x-ray production and damaging to tube
self rectification
- Produces a DC waveform similar to self-rectification
- Employs single rectifier in circuit
- Protects x-ray tube from acting as a diode rectifier
o Protection is marginal - Inefficient x-ray production
- Utilized in very inexpensive x-ray units
o Veterinary
o Podiatric
Half-Wave Rectification
Takes advantage of both phases of alternating current
* Provides only DC to x-ray tube
* Uses at least four rectifiers in a bridge rectification circuit
* Most efficient form of current for x-ray production
o All modern equipment is full-wave rectified
Full-Wave Rectification
Electrical process of liberating electrons from a wire filament
* Filament is heated to very high temperature, due to its resistance
o Filament is typically tungsten
* “Boiling off” electrons create an electron cloud around filament
* Principle of an incandescent light bulb
* Very important to x-ray tube design
thermionic emission
what current does the electrons flow in one direction
direct current
The flow of electrons in an electrical circuit
current
what current does the electrons move back and forth
Alternating current
what current does transformers use?
Alternating current
difference in charge
voltage
what current does step up and step down transformers function on
alternating current
what is the rectifier located in between
step up and xray tube
number of distinct wave cycles
phase
number of voltage pulses per cycle
pulse
number of pulses
frequency
where there is more turns on primary compared to secondary is it step down or step up
step up
what is the turns ratio
N(secondary) / N(primary)
first of three transformers in xray circuit
autotransformer
can increase or decrease voltage and amps
can be step up or step down
small changes
adjustable
autotransformer
An electrical component that inhibits the flow of current through a circuit
designed to reduce current flow through a circuit
decreases voltage
resistors
a unit of measure of the degree of resistance between two points of a conductor within a circuit
ohms
also referred to as intensity and measure of electrical current
amperage
provides electrical potential /power
voltage
the resistance of the particles to flow within a circuit
ohms
the force given to each particle to move
voltage
all parts or circuit elements are connected in a continous line
any break causes the circuit to fail
series
its current is able to flow beyond its continuous line , a break in parallel circuit still allows it to function
parallel circuit
change the voltage (polarity) in an electrical circuit
increase or decrease voltage
transformers
transformers have three parts:
iron core
primary coil (electricity in)
secondary coil (electricity out)
polarity of voltage rapidly changes back and forth
unrectified
electrons flowing in the reverse direction are blocked
rectified
which rectification is described :
the gap between pulses has no electron flow and the other wave is blocked
half wave rectification
which rectification is described :
all electrons flow in the same direction
back flowing electrons are not blocked (their polarity is changed so they flow in the same direction)
no gaps between pulses, but wave drops to 0
full wave rectification
work by self induction
do step up and step down
make only small changes
has only 1 coil around a single coil
autotransformer
