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# Rad 121 Chapter 5 Electricity, Magnetism, and Electromagnetism

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x-ray imaging system coverts ____ into ____
electric energy into electromagnetic energy
the study of stationary or fixed electric charges is known as?
electrostatics
what are the five laws of electrostatics?
1)concentration
2)distribution
3)attration/repulsion
4)inverse square law
5) movement
Repulsion/attraction Law:
like charges______
unlike charges_____
repel; attract
force between 2 charges is directly proportional to the product of their charges and inverserly proportional to the square of the distance between them is known as?
Coulombs Law
Charges reside on the external surface of conductors is known as?
Distribution Law
Concentration Law: greatest distribution of charges on surface on ________ curve?
sharpest/roughest
process of electric charges being added/subtracted from an object is known as what?
electrifrication
objects rub against one another and electrons travel from one to the other is known as?
friction
two objects touch; electrons move from one object to another is known as?
Contact
Contact causes _______ of charges?
equalization
process of electrical fields acting on one another w/o contact is known as?
Induction
it is the most important method?
induction
induction method used in the operation of _______devices?
electronic
study of electric charges in motion is known as?
electrodynamics
movement of electrons or electricity results from the traveling of ______?
electrons
only _____ charges move along solid conductors
negative
Positive charges are fixed in the ?
nucleus
electrons move from _____ to _____ concentration
highest to lowest
______charge=object with more electrons
Negative
_____charge=object with weaker negative charge or an object with fewer electrons than another object
positive
electric current travels from _____ to _____ poles
postive to negative
electric /electron flow travels from ____ to ____ poles
negative to positive
electric current occurs in:
1)vacuum (x-ray tube)
2)neon gas
3) inonic solutions & metals
any substance through which electrons flow easliy is known as?
a conductor
Examples of conductors:
1)copper wire
2)aluminium
3)water
materials that resist electron flow is known as?
insulator
good insulators are:
1)rubber
2)plastic
3)glass
materials with the ability to conduct electricity under certain conditions and insulate under other conditions is known as?
semiconductors
Two examples of semiconductors are:
silicon and germanium
allows electrons to flow freely w/no resistance below certain temperatures is known as?
superconductivity
superconductivity works with what kind of temepratures?
very cold (liquid nitrogen)
two examples of superconductivity is?
noibiun and titanium wire which are used in MRI
Nature of electron flow is?
1)direction of electron travel
2)quantity of electrons flowing
3)force of electron travel
4)opposition to current flow
what are the two currents for direction of electron flow?
Direct current (DC)
Alternating current (AC)
all electrons travel in the same direction is what type of current?
Direct
oscillating current is what type of current?
Alternating
Quantity of electrons flowing=
current
quantity is measured in what unit of current?
Ampere = A
x-ray is measured in what unit?
mA
causes number of electrons and x-rays produced to vary is known as what?
mA
force of electron tavel=
electric potential
electric potential exists when the flow of electrons has?
stopped
unit of electric potential is?
volt, V
electric potential determines the speed of electrons that determines penetrability which developes what?
contrast
amount of opposition to current flow is =
resistance or impedance
opposition is measured in
Ohms
unit of resistance is called?
Ohm
what are the 3 factors that impede the flow of electrons?
1)Length of the conductor
2)crosssectional diameter of the conductor
3)temperature of the conductor
Length of the conductor-as length doubles, resistance does what? and has what proportional relationship?
doubles, directly
crosssectional diameter of the conductor-as diameter doubles, resistance does what? and has what type of relationship
halved, inversely
temperature of the conductor-
causes increase or decreases of resistance depending on conductor, insulator or semiconductor
electric potential is sometimes called
voltage
unit of electric potential is
volt (V)
V for US household is
110V
Electric power is known as
rate of doing
Electric power is measured in
watts (w)
electric power-Household appliances tend to operate between
500 to 1500w
x-ray machines require kW (electric power)
20 to 150kW
x-ray machines require V (electric potential)
220V
Ohm's law is a interrelationship of
current, potential, and resistance
for Ohms law voltage across the total circuit is equal to the
current x resistance
what is the Ohms law equation
V=IR
V=
electric potential in volts
I=
current in amperes
R=
resistance in ohms
electric power formula
P=current x voltage
formed by controlling the resistance in the closed path of a conductor is known as?
electric circuits
all circuit elements are conected in a line are known as
series circuit
what are some advantages to series circuits?
cheap, easy to fix, repair, replace. greater potential difference=greater total voltage. current remains the same
what are some disadvantages to series circuits?
all resistances have to be operable. failure of one=the whole supply. resistance increases
each element has an individual branch is known as
parallel circuit
what are some advantages to parallel circuits?
elements can operate at lower voltage bc voltage doesnt change. failure of one element doesnt interrupt the other . resistance goes down
whart are some disadvantages to parallel circuits?
what are 2 safeguards that break the circuit before a dangerous temeprature is reached?
fuse, circuit breaker
metal tab that melts with increased heat is known as?
fuse
pops open and can be reused and reset
circuit breaker
the voltage across the total circuit or any portion of the circuit is equal to the current time the resistance
Ohm's Law
Ohm's Law equation
V=IR
I=V/R
R=V/I
semiconductor
A material that when combined with some other material can be turned into an insulator or a conductor.
conductor
a substance that readily conducts e.g. electricity and heat
insulator
a material that does not allow heat or electrons to move through it easily
what is the coulomb's law equation?
F=k Q^AQ^B/d^2