electricity Flashcards
(119 cards)
1
Q
supplied to the X-ray imaging
system to be converted into electromagnetic
energy
A
Electric energy
2
Q
• It is the set of phenomena associated with the presence and
motion of matter that has a property of electric charge.
A
electricity
3
Q
• It is the presence and flow (movement) of charge.
A
Electricity
4
Q
It is sometimes used to mean “electrical”.
A
Electricity
5
Q
It is the basic property of matter carries by some elementary
particles
A
electric charge
6
Q
It comes into two types: positive (+) and negative (-)
A
Electric charge
7
Q
The unit of charge is_____
which was named after Charles-
Augustin de Coulomb (eminent
French Physicist)
A
Coulomb
8
Q
• The unit of charge is Coulomb
which was named after _______ (eminent
French Physicist)
A
Charles-
Augustin de Coulomb
9
Q
One (1) Coulomb =
A
6.24x 1018 electron charges
10
Q
The smallest unit of “free” charge known in nature is the charge of an
electron or proton which has a magnitude of
A
1.602 x 10-19 C
11
Q
Electric charges associated with electrons and protons have the same magnitude but opposite signs
A
12
Q
• It states that “the electrical force
between two charged objects is
directly proportional to the product of
the quantity of charge on the objects
and inversely proportional to the
square of the separation distance
between the two objects”.
A
Coulomb’s law
13
Q
• Fe = electric force
• k = Coulomb constant (9 x 109 Nm2/C2)
• q1 = charge on object 1
• q2 = charge on object 2
• r = distance between charges
A
Coulomb’s law
14
Q
It is a force that acts at a distance,
even when objects are not in contact
with one another
A
Electrostatic force
15
Q
The action at a distance means that
one charge creates a field which in
turn acts on the other charge
A
Electrostatic force
16
Q
This provides a convenient graphical presentation of
the electric field in space
A
Electric field lines
17
Q
the direction of the field lines is outward for
A
positive charge
18
Q
the direction of the field lines is inward for
A
negative charge
19
Q
Three Ways for a Neutral Object to be Charged
A
- Friction
- Conduction
- Induction
20
Q
Occurs when two different
materials rub against each other
causing the transfer of electrons
A
friction
21
Q
the opposing force
which acts in the opposite
direction of the movement of the
upper body
A
friction
22
Q
Occurs when a neutral object is
placed in contact with an already-
charged objec
A
conduction
23
Q
a
charged object is brought
near but not touched to a
neutral conducting object.
A
induction
24
Q
The presence of a charged
object near a neutral
conductor will force (or
induce) electrons within the
conductor to move.
A
induction
25
Four (4) Electric States of Matter
• Superconductor
• Conductor
• Semiconductor
• Insulator
26
No resistance to electron flow, no
electric potential required, and must
be very cold
Superconductor
27
The critical temperature usually
between
absolute zero and 10 Kelvin
(-273 Celsius and -263 Celsius or as
high as 125 Kelvin (-148 Celsius)
28
are
used in machines for nuclear
magnetic resonance (NMR) in
hospitals and in the orientation
of the beam of a particle
accelerator.
Superconductor
29
substance in which electrical
charge carriers (usually
electrons), move easily from
atom to atom with the
application of voltage
conductor
30
copper, aluminum
conductor
31
It is a material that does not
conduct electrical current
insulator
32
These materials include paper,
plastic, rubber, and glass.
insulator
33
A solid substance that has a
conductivity between that of an
insulator and that of most metals
SemiConductor
34
Devices made of semiconductors,
notably silicon, are essential
components of most electronic
circuits
SemiConductor
35
It is defined as the ____ ______ energy, U , per unit charge
Electric potential (V)
36
Electric potential (V) formula
V = U/q
37
Sometimes referred to as the voltage
Electric potential (V)
38
The higher the voltage, the greater the potential to do work
39
It is an electromotive force or potential difference expressed in
volts
voltage
40
The Volt unit is named after _______, an Italian
physicist who invented an electric battery
Alessandro Volta
41
1 V =
1 J/C
42
It is the rate of flow of electrons in a wire.
Electric Current
43
si unit of electric current
Ampere (A)
44
SI Unit is Ampere (A) which was named after
Andre Marie
Ampere
45
Electric Current: 1 A is the flow of electric charge across a surface at the rate of
1C/s
46
• It is a measure of opposition to the flow of electric current
• The inverse is electrical conductance
Electric Resistance
47
si unit of Electric Resistance
ohm Ω
48
Electric resistance SI unit is Ohm (Ω), named after a German physicist and mathematician?
Georg Simon Ohm
49
• “The amount of electric current through a metal conductor
in a circuit is directly proportional to the voltage applied
across it and inversely proportional to the resistance”
ohm’s law
50
Power is a measure of energy per unit time.
Electric Power
51
measure of energy per unit time.
power
52
gives the rate of energy consumption or production.
power
53
The units for power are generally
watts or W
54
• P = IV
• P = I2R
electric power
55
• P –power in Watts (W), I –electric current in Ampere (A), R –electric
resistance in Ohm (W), and V –voltage in Volts (V)
56
The amount of electrical energy transferred to a device depends on its power and the length of time it is switched on.
57
Electric energy is measured in
kilowatt-hours, kWh.
58
E = P x t
electric energy
59
a fundamental property of some forms of matter.
magnetism
60
Some objects are known to attract iron fillings. These phenomena is
called
magnetism
61
A charge particle in motion also creates
magnetic field
62
In radiologic sciences, understanding magnetism is important in
__________ which uses powerful magnetic fields to
create images of the human body.
magnetic resonance imaging
63
vector field
that describes the magnetic influence of electrical currents
and magnetized materials.
magnetic field
64
The motion of orbital electrons
and their spins, in opposite direction produce
tiny magnetic fields
65
also created by a moving electric charge
magnetic field
66
• SI Unit of magnetic field (B) is Tesla (T)
• 1 Tesla = 1 Ns / Cm (Newton second per Coulomb meter
• Magnetic field (B) is also measured in Gauss (G)
• 1 T = 10,000 G
magnetic field
67
SI Unit of magnetic field (B) is
Tesla T
68
Magnetic field (B) is also measured in
Gauss (G)
69
1 T =
10000 G
70
is dipolar (magnetic dipole). It has a
north and south pole.
Magnetic field
71
are regions at the end of the magnet where the magnetic field are strongest
Poles
72
Like magnetic poles
repel
73
unlike magnetic poles
attract
74
a region
created by the accumulation of
many atomic magnets with their
dipoles aligned.
Magnetic domain
75
This means that the individual
magnetic moments of the atoms
are aligned with one another,
and they point in the same
direction.
Magnetic Domain
76
a consequence of the electromagnetic force,
one of the four fundamental forces of nature, and is caused by the
motion of charges.
Magnetic Force
77
The magnetic force is a consequence of the electromagnetic force,
one of the four fundamental forces of nature, and is caused by the
motion of charges.
78
magnetic force : Two objects containing charge with the same direction of motion have
a magnetic attraction force between them.
79
magnetic force: objects with charge moving in opposite directions have
a
repulsive force between them
80
Like poles repel, unlike
poles attract
Magnetic Law
81
As moving charges create magnetic fields, so they
experience forces from magnetic fields generated by
other materials. The magnitude of the force experienced
by a particle traveling in a magnetic field depends on
the charge of the particle (q), the velocity of the particle(v),
the strength of the field(B), and, importantly, the angle
between their relative directions(θ):
Lorentz Force
82
described by the Lorentz Force Law
magnetic force
83
Example is the Earth.
Lodestone has been
exposed to Earth’s
magnetic field for a long
time and has developed a
strong magnetism.
Natural magnets
84
Usually made of iron.
Made by aligning their
domains in the field of an
electromagnet.
Permanent magnets
85
Consists of
wire wrapped around an iron
core. When electric current
is conducted through the
wire, a magnetic field is
created.
Electromagnets
86
Materials
that are unaffected by
magnetic field
Nonmagnetic
87
Materials that are
weakly repelled by magnetic
fields. They cannot be artificially
magnetized, and they are not
attracted to a magnet.
•Ex. Copper, beryllium, lead
Diamagnetic
88
Materials that lie
somewhere between
ferromagnetic and nonmagnetic.
They are slightly attracted to a
magnet and loosely influence by
an external magnetic field.
Paramagnetic
89
Gadolinium -contrast agents
used in MRI, platinum,
aluminum
Paramagnetic
90
Strongly
attracted to magnets or
magnetic materials and usually
can be permanently magnetized
by exposure to a magnetic field.
Ferromagnetic
91
Alnico –combination of
aluminum, nickel, cobalt
Ferromagnetic
92
a process where a
magnetic field is created by
introducing a current into the
conductor or by producing electricity
with changing magnetic field
Electromagnetism
93
a branch of
Physics that deals with the
electromagnetic force that occurs
between electrically charged particle
Electromagnetism
94
a type of physical interaction
that occurs between electrically charged particles.
Electromagnetic force (EMF)
95
It acts between charged particles and is the
combination of all magnetic and electrical forces.
Electromagnetic force (EMF)
96
can be attractive or
repulsive.
electromagnetic force
97
Any charge in motion induces a
magnetic field
98
Electrons flowing in a wire creates a
magnetic field
99
represented by the
imaginary lines that form concentric
circles centered on the wire.
magnetic field
100
overlap inside
the loop because the wire is curved
magnetic field lines
101
All the magnetic field lines come
together at the ____ of the loop
making the magnetic field strong
center
102
A coil of wire is called a
solenoid
103
The magnetic field can be
intensified by wrapping the
coil of wire around
ferromagnetic material
(iron).
104
a current-
carrying wire wrapped around an
iron core, which intensified
electromagnet
105
The _____ intensifies the
magnetic field.
iron core
106
discovered
that electric currents create
magnetic fields.
Hans Christian Ørsted(Danish
physicist and chemist)
107
In 1831, formulated two laws on bases of his experiments
Michael Faraday
108
Whenever a conductor are
placed in a varying magnetic field, an
electromotive force (emf) is induced. If the conductor circuit is closed, a current is
induced which is called induced current
first law
109
Faraday’s concluded that an electric current cannot be induced in a circuit merely by presence of magnetic field.
• It should be a changing magnetic field.
110
The magnitude of
the induced emf in a coil is equal
to the rate of change of flux that
linkages with the coil.”
second law
111
the product of
the number of turns in the coil
and the flux associated with the
coil.
flux linkage
112
proposes a Theory of Electromagnetic
Filed which has something to do with the space in the neighborhood of the electric or magnetic bodies
James Clerk Maxwell
113
that part of space which contains
and surrounds bodies in electric or magnetic conditions
Electromagnetic field
114
are waves that
are created as a result of vibrations between an
electric field and a magnetic field
Electromagnetic waves or EM waves
115
a form of energy that is
produced by oscillating electric and magnetic
disturbance, or by the movement of electrically
charged particles traveling through a vacuum or
matter.
Electromagnetic energy
116
The electric field and magnetic field of
an electromagnetic wave are
______ to each
other. They are also perpendicular to
the direction of the EM wave.
perpendicular
117
can travel through anything –air, solid material or
even in a vacuum
EM waves
118
cannot be deflected by electric field nor magnetic field.
EM waves
119
EM waves travel at the speed of light through empty space.
• Speed of light = 3x108meters/sec or 186,000 miles/sec
EM waves travel in a form of transverse wave.
EM are classified according to their frequency and
wavelength.
