Exam 1 Ch 5- electricity, magnetism, & electromagnetism Flashcards
1
Q
electrodynamics-
A
study of charges in motion
2
Q
electric current/electricity-
A
when an electric potential is applied to some objects, electrons move along the object
3
Q
electrodynamics aka-
A
electric current
4
Q
electron currency is caused by-
A
flow of electrons
5
Q
electric current is the opposite direction of-
A
electron flow
6
Q
conductors-
A
any substance that allows electrons to flow easily
7
Q
most metals are-
A
conductors
8
Q
water is a good conductor because-
A
because of the salts & other impurities
9
Q
conductors & insulators obey-
A
olms law
10
Q
insulators allow electrons to-
A
flow freely whereas conductors do not
11
Q
insulators-
A
any substance that doesn’t allow electrons to flow
12
Q
examples of insulators-
A
-glass
-clay
-rubber
13
Q
semiconductors-
A
-acts like insulators under some conditions & conductors under other conditions
-not affected by temperature
14
Q
semiconductors ex-
A
sillicone
15
Q
superconductivity-
A
at a certain temperature, material has no resistance, so it allows electrons to flow feeely
16
Q
superconductivity ex-
A
titanium
17
Q
circuit-
A
when a conductor has an electric current & controlled resistance & forms a closed path
18
Q
since electrons flow on the surface of wires in an electric circuit, as the diameter of the wire decreases, resistance to flow-
A
increases
19
Q
electric current in an electric circuit is measured in-
A
amperes
20
Q
Ohm’s law-
A
-voltage across the total circuit or any portion of the circuit is equal to the current times the resistance
-voltage- V = IR, R = V/I, I = V/R
21
Q
series circuit-
A
-all elements are connected along the same conductor
-voltage is the sum of all circuits
-current is the same everywhere
-I is constant
22
Q
rules for a series circuit-
A
-RT = R1 + R2 + R3
-IT = I1 + I2 +I3
-VT = V1 + V2 + V3
-R- resistance
-T- total resistance
-I- constant
-V- voltage
-A- current
23
Q
____ is access point where charge begins in a series circuit-
A
battery
24
Q
parallel circuits-
A
-contains elements that bridge conductors
-voltage is the same everywhere
25
rules for parallel circuits-
-1/RT = 1/R1 + 1/R2 +1/R3
-IT = I1 + I2 + I3
-VT = V1 + V2 + V3
26
direct current-
current flowing in only one direction
27
altering current-
current in which electrons oscillate
28
electric power is measured in-
watts
29
1 watt =-
1 amber flowing through a potential of 1 V
30
magnetism discovered in-
magnesia
31
magnetism-
-magnetic oxide of iron
-naturally occurring & used as a compass
-fundamental property of some forms of matter
32
magnetism-
-magnetic oxide of iron
-naturally occurring & used as a compass
-fundamental property of some forms of matter
-fundamental form of nature (always existed)
33
any charged particle in motion creates-
magnetic field
34
magnetic field is-
-perpendicular to motion of the charged particle
-can be predicted in which way it's going to go
35
magnetic fields-
are bipolar or dipolar
-indicates no matter what, wherever that field exists, both holes are represented
-have a north (positive) & south (negative) poles
36
magnetic dipole-
electrons rotating on their axis create a magnetic field
37
magnetic domain-
accumulation of these forms a magnetic domain
38
if all magnetic domains in an obj. are orientated the same way, then-
the object will act like a magnet
39
classification of magnets (4)-
-natural magnets
-artificially induced magnets
-electromagnets
-temporary magnets
40
natural magnets found-
in earth
41
artificially induced permanent magnet-
-usually iron
-non-magnetic materials placed in a strong magnetic field
-any item that has their domain aligned w: the field of an electromagnet
42
electromagnets ex-
wire wrapped around an iron core
43
temporary magnet-
artificially induced magnet
44
magnet classification of matter (6)-
-magnetic permeability
-non-magnetic
-diamagnetic
-paramagnetic
-ferromagnetic
-magnetic susceptibility
45
magnetic permeability-
ability to attract magnetic field lines
46
non magnetic-
unaffected by magnetic field
47
diamagnetic-
weakly repelled by both poles
48
paramagnetic-
weakly attracted to both poles
49
ferromagnetic-
strongly attracted by magnetic fields (most metals- soft irons)
50
magnetic susceptibility-
ease at which materials can be changed into a magnet
51
magnetic laws-
-smallest unit of magnetism impossible to define
-dividing any magnet just makes smaller magnets
-every magnet has 2 poles : north (similar to positive) & south (similar to negative)
-closed loops cannot break it off
52
ferromagnetic material can be made into a magnet by-
induction
53
if a material doesn't retain magnetic property after removal from an external magnetic field, it is-
a temporary magnet
54
low stone is-
naturally magnetic
55
electromagnetism-
force associated w: electrons in motion
56
fundamental forces of nature in electromagnetism-
-gravity
-strong nuclear force
-weak nuclear reaction
57
electricity & magnetism are-
different aspects of the same force
58
scientist believed electricity & magnetism were-
2 separate forces
59
research was limited because-
electricity couldn't be produced & controlled
60
research was restricted to-
electrostatics
61
method of producing flow of electrons stimulated investigations of-
electricity & magnetism
62
Galvani discovered-
a frogs leg twitched when touched by 2 different metals (similar to electrostatic charge)
63
Alessandro Volta-
used this to experiment w: other metals to induce an electric current
64
voltic plates-
stacked zinc & copper plated & produced a weak electric current
65
modern batteries used-
a carbon rod as a + electrode & a zinc cylindrical can (-) filled w: electrostatic paste
66
source of EMF (Electromagnetic Force)
any device that converts energy directly into the electric energy
67
Oersted's Experiment-
-in 1820 Hans Oersted used a straight wire adjacent to a free rotating compass
-when no current was flowing, the compass pointed north
-when current was flowing, compass pointed straight at wire
68
if a charge is in motion, a magnetic field is-
induced
69
right hand rule-
applies to solenoids
70
solenoid-
coil of wire
71
inside the loop of the coil of the magnetic field lines are-
concentrated
72
,magnetic field lines of a solenoid are stronger-
inside the coil
73
magnetic field can be further intensified by-
putting a ferromagnetic material inside the solenoid
74
Faraday's first law-
law of electromagnetic introduced
75
if an electric current induces a magnetic field, then does a magnetic field induce an electric current?
no, it has to be in a changing magnetic field
76
animeter-
measures amps
77
changing magnetic field-
magnetic field that changes its intensity or direction
78
the current magnitude depends on 4 things-
-strength of the magnetic field
-velocity of the magnetic field as it moves past the conductor (how fast you move the magnet)
-the angle of the conductor to the magnetic field
-number of turns in the conductor (turns ratio)
79
turns ratio-
number of turns in a conductor
80
parallel circuits have the greatest-
magnitude/strength of currents
81
changing magnetic fields can be produced 3 ways-
-magnet moved near a coil of wire
-coil of wire moved near a stationary magnet
-if electromagnet is used, then both magnet & solenoid can be fixed & current & the electromagnet can be varied
82
changing magnetic field ex-
radio reception
83
changing magnetic fields can induce-
current (A/C current)
84
Lenz's law-
2nd law of electromagnetics
85
lenz's law determined-
how to tell the direction of induced current flow
86
magnetic field induced-
opposes a field that induced it (in other words, north induces north)
87
2 basic types of electromagnetic induction-
-self induction
-mutual induction
88
self induction-
induction of an opposing magnetic field in a single coil by its own changing magnetic field
89
mutual induction-
generation of an altering current in a secondary coil by supplying & alternating current to the primary coil
90
only difference b/w self & mutual induction-
the number of solenoids
91
electromagnetic devices-
-application derived from Oersted/s & Faraday's experiments
-electric generator, electric motor, & transformer
92
electromechanical devices is a practical use of-
mutual induction
93
in an electric generator, mechanical energy is converted to-
electrical energy
94
in an electric generator, mechanical energy can be supplied by-
hand, wind, water, & heat
95
simple generators produce-
alternating current
96
an electric generator w: a commuter ring-
A/C is changed to pulsating D/C
97
electric motors convert electric energy to-
mechanical energy (rotation)
98
current motor-
simple form
99
induction motor used in most-
x-ray tubes
100
rotators & stators-
both are solenoids
101
stator electromagnets-
coils of wire that are stationary
102
stationary rotators can-
can move
103
the transformer-
transforms electric potential & current
104
the transformer consists of-
solenoids w: ferromagnetic material in the center
105
if ferromagnetic material is shaped like a magnetic field, then it is said to have-
good coupling
106
job of the transformer-
transform voltage
107
the transformer uses-
mutual induction
108
voltage on the secondary/induced side of the transformer-
is directly proportional to the ratio of the number of turns of secondary coil to the number of turns in the primary side
109
transformer law-
Vs/Vp = Ns/Np (Ns/Np is called turns ratio)
110
step-up transformer-
-turns ratio greater than 1
-speeds up voltage
-current decreases
111
step-down transformer-
-turns ratio less than 1
-top number smaller than bottom number
-slows down voltage
-current increases
112
transformer inefficiency-
loss of efficiency is minimal
113
3 main causes of efficiency loss in the transformer-
-resistance- due to heat & Ohm's law
-hysteresis- due to changing magnetic field
-eddy currents- due to lenz's law
114
types of transformers (4)-
-autotransformer
-closed-core
-open-core
-shell-type
115
autotransformer-
basically a transformer that has primary & secondary connections, but only has 1 solenoid
116
closed-core-
more efficient than open-core
117
shell-type-
most efficient type & most commonly used
