Ch 4 Flashcards
1
Q
Electrostatics
A
Stationary electric charges
2
Q
Electromagnetic induction
A
Transferring electric potential energy from 1 position to another (transformer)
3
Q
Electrodynamics
A
Electric charges in motion
4
Q
xray imaging system
A
Covert electric energy into electromagnetic energy
5
Q
Electric energy
A
well controlled electric current
6
Q
Electric charge units
A
Positive or negative
7
Q
Discrete
A
Apart or detached from others, separate, distinct
8
Q
Discussions of electric charge
A
Deal with negative electric charges associated with electrons
9
Q
Electrons
A
1 unit of negative charge
10
Q
Protons
A
1 unit of positive charge
11
Q
Electrification
A
too many or too few electrons- created by contact, friction, induction
12
Q
Static electricity
A
Removal of electrons which causes the object they were removed from to be electrified
13
Q
Rubbing feet on carpet
A
Build up of electrons causes you to become electrified
14
Q
Why does hair stand up when rub balloon
A
Negatively charged particles are repulsed from each other. Trying to get away from other negative charged hairs.
15
Q
When running combs through hair
A
Comb picks up electrons becoming negatively charged
16
Q
How can a comb pick up paper
A
Excess electrons on comb repel electrons in paper causing edges of paper to become positively charged. Neg comb & pos paper are attracted to each other.
17
Q
Electric ground
A
Earth can accept excess electric charges
18
Q
During thunder storm
A
Electrons can be moved from 1 cloud to another. 1 cloud= positive and 1= negative. Return to normal state= lightning between clouds and earth.
19
Q
Coulomb
A
1c= 6.3*10 ^18
20
Q
Unlike charges
A
attract
21
Q
Like charges
A
repel
22
Q
coulomb’s law
A
electrostatic force is directly proportional to product of electrostatic charges. Inversely to square of distance.
23
Q
Electric charge distribution
A
uniform throughout or on surface
24
Q
electric charge of conductor
A
concentrated along sharpest curvature of surface
25
electric field
associated with an electric charge. positive points outward, negative points inward.
26
uncharged particles
don't have an electric field
27
magnetic field of like charges
will cause objects to be physically repulsed from 1 another
28
magnetic field of unlike charges
pulls toward one another. negative- inward, positive- outward
29
electrostatic force
directly proportional to product of electrostatic charges
30
more charges that are present
stronger the force will be
31
electrostatic force
inversely proportional to square of the distance between them
32
AS distance increase
electrostatic force decreases
33
electric charge distribution is uniform
throughout or on decreasing surface
34
surface of copper wire
electric charges are distributed evenly on surface
35
electric charge of conductor
concentrated along sharpest curvature of surface
36
electric cattle prod
charges will be concentrated at surface
37
Electric charges
unit is volt, have potential energy, can do work. 1v=1j/c
38
electrodynamics
study of electric charges in motion
39
electric potential applied to copper wire
electrons will move along the wire. called electric current or electricity
40
electric current is opposite
of electric flow
41
electron/ currents move
electrons ----->
| <-------- currents
42
conductor
substance through which electrons flow easily. metal, water
43
insulator
material that doesn't allow electric flow. glass, clay
44
semiconductor
material under some conditions behave as insulator and under some behaves like conductor
45
Superconductivity
allow flow of electrons without resistance at or below critical temp.
46
electric circuit
path of electron flow from generating source through components & back again
47
current
flow of electrons measured in amperes
48
Electric potential
measured in volts, work required to move charges
49
resistance
opposition to force measured in ohms. changing size of wire electrons flow through varies resistance of circuit
50
resistance _____, current ______
increase, decreases
51
Ohm's law
voltage across circuit equal to current times resistance
52
V=
IR
53
R=
V/I
54
I=
V/R
55
series circuit
all circuit elements are connected in a line along same conductor
56
parallel circuit
elements are connected at ends rather than lying in a line along conductor
57
current though each circuit
equal to total circuit current
58
sum of voltage across circuit
equal to total circuit voltage
59
total resistance
equal to sum of all resistances. inverse of sum of reciprocals of each individual resistance
60
total circuit current
sum of current through each circuit element
61
circuit voltage
voltage across each circuit element is equal to
62
xmas lights
can be series or parallel. series- 1 light out, all lights go out. parallel- 1 light out, others still on
63
direct current
electrons flow in one directions- straight line. horizontal axis- time, vertical axis- voltage
64
alternating current
electrons go back & forth. sin wave 0 at rest, 1 highest point, 2 shift direction, 3 max at lowest point
65
electric power
measured in watts (W)
household- 500-1500W
xray- 20,000-150,000W
66
1 watt=
1 A though 1 V
67
power=
power (W)=voltage (V)*Current (A)
W=V*A
68
V=
IR
69
P=
1V=IIR=1^2R
70
walk north
find water
71
charged particle in motion
creates magnetic field (difficult to detect & measure)
72
as electrons rotate around nucleus of atom
magnetic field lines are perp to plane of motion
73
magnetic field is neutralized
in electron pairs
74
Atoms with odd # in shells
small electric field
75
continuous field
bipolar or dipolar
76
magnetic dipole
current that flows in small loop
77
magnetic domain
accumulation of atomic magnets with their dipoles aligned- acts like a magnet
78
magnets
classified according to origin of magnetic property
79
natural magnets
earth, lodestones
80
artificially induced magnets
iron bar, compass
81
current conducted through electric wire
magnetic field is created. intensity proportional to current
82
ferromagnetic
materials strongly attracted and can be permanently magnetized through induction. iron, cobalt, nickel
83
diamagetic
materials weakly repelled by either magnetic pole- water, plastic
84
paramagnetic
materials slightly attracted to a magnet
85
nonmagnetic
materials unaffected by magnetic field- wood, glass
86
induction
materials can be made magnetic
87
distance between magnets halved
magnetic force increases 4 times
88
attraction of compass
increases as it draws closer to north pole
89
SI unit for magnetic field
telsa (T)
90
Alessandro Voltra
stacked zinc & copper plates to produce a weak electric current
91
modern batteries
use positive carbon rod as an electrode surrounded by electrolytic paste in negative zinc cylinder
92
electric energy
any device that converts some form of energy
93
electric potential measured
in volts or j/c
94
oersted
discovered link between electric & magnetic forces. Electric current produced a magnetic field.
95
charge in motion
produces a magnetic field
96
stationary charges
don't produce a magnetic field
97
as electrons travel through wire
produce magnetic field without voltage to push through.
98
magnetic field lines form
concentric circles around wire.
99
more loops of wire stacked
intensity increases
100
solenoid coil wire
magnetic field concentrated through center
101
ferromagnetic material in center of solenoid
magnetic field is stronger
102
electromagnet
current carrying coil of wire wrapped around an iron core- intensifies
103
magnetic field can be varied by
adjusting the current
104
magnetic field can be turned off
by turning off the current
105
Michael faraday
discovered that stationary magnet won't induce an electric current but changing magnetic field will
106
ammeter
measure electric current in coiled wire with stationary magnetic field
107
electromagnetic induction
electric current is induced in circuit if some part is in changing magnetic field
108
as current changes
so does strength of magnetic field
109
magnitude of induced current depends on (4)
1. strength of magnetic field
2. velocity as it moves past conductor
3. angle of field to conductor
4. # turns in conductor
110
varying magnetic field intensity
induces an electric current
111
electric motors operate
because electric current produces mechanical motion
112
electric generators
electric current produced based on changing magnetic field
113
coil rotated by mechanical energy
hand, steam, water
114
current induced in coil wire
wire is moving in magnetic field
115
electric motor has same
components but works differently
116
electric current produces
mechanical motion
117
induction motor powers
rotating motor of xray rube
118
stators
stationary electromagnets
119
rotor shaft
made of copper and soft iron
120
electromagnets energized in sequence
rotor rotates in response to magnetic field- attempt to align with magnetic poles
121
transformer changes
intensity of alternating voltage and current
122
motor changes electric energy to____. Generator changes _____ to electric
mechanical
123
transformer doesn't change
type of energy but transforms electric current & voltage into higher/lower intensity
124
1 coil wrapped around loop
magnetic field tends to be confined to loop
125
2nd coil in iron loop
magnetic field by 1st follows loop passing through secondary coil
126
primary coil
produces magnetic field
127
secondary coil
produces electric current from magnetic field produced by primary wire
128
changing current in primary coil
changes current in secondary coil
129
transformer is used to change
voltage & current in an AC circuit
130
change in voltage is ___ proportional to ratio of # of windings in secondary coil to primary
directly
131
transformer law
vs/vp=ns/np=ip/is
132
vs
secondary voltage
133
vp
primary voltage
134
ns
turns in secondary
135
np
turns in primary
136
step up transformer
ratio greater than 1, increase voltage, current reduced
137
step down transformer
ratio less than 1, decrease voltage, current increased
138
voltage ___ current halved
doubled
139
voltage ____ current doubled
halved
140
voltage & current have ____ relationship
inverse
141
autotransformers
small, primary & secondary coils connected
142
shell type transformer
secondary coil wrapped around primary coil
