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Radt. 3011 > Exam 1 Ch 5- electricity, magnetism, & electromagnetism > Flashcards

Exam 1 Ch 5- electricity, magnetism, & electromagnetism Flashcards

1
Q

electrodynamics-

A

study of charges in motion

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2
Q

electric current/electricity-

A

when an electric potential is applied to some objects, electrons move along the object

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3
Q

electrodynamics aka-

A

electric current

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4
Q

electron currency is caused by-

A

flow of electrons

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5
Q

electric current is the opposite direction of-

A

electron flow

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6
Q

conductors-

A

any substance that allows electrons to flow easily

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7
Q

most metals are-

A

conductors

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8
Q

water is a good conductor because-

A

because of the salts & other impurities

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9
Q

conductors & insulators obey-

A

olms law

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10
Q

insulators allow electrons to-

A

flow freely whereas conductors do not

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11
Q

insulators-

A

any substance that doesn’t allow electrons to flow

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12
Q

examples of insulators-

A

-glass
-clay
-rubber

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13
Q

semiconductors-

A

-acts like insulators under some conditions & conductors under other conditions
-not affected by temperature

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14
Q

semiconductors ex-

A

sillicone

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15
Q

superconductivity-

A

at a certain temperature, material has no resistance, so it allows electrons to flow feeely

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16
Q

superconductivity ex-

A

titanium

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17
Q

circuit-

A

when a conductor has an electric current & controlled resistance & forms a closed path

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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

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19
Q

electric current in an electric circuit is measured in-

A

amperes

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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

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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

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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

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23
Q

____ is access point where charge begins in a series circuit-

A

battery

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24
Q

parallel circuits-

A

-contains elements that bridge conductors
-voltage is the same everywhere

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25
Q

rules for parallel circuits-

A

-1/RT = 1/R1 + 1/R2 +1/R3
-IT = I1 + I2 + I3
-VT = V1 + V2 + V3

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26
Q

direct current-

A

current flowing in only one direction

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27
Q

altering current-

A

current in which electrons oscillate

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28
Q

electric power is measured in-

A

watts

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29
Q

1 watt =-

A

1 amber flowing through a potential of 1 V

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30
Q

magnetism discovered in-

A

magnesia

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31
Q

magnetism-

A

-magnetic oxide of iron
-naturally occurring & used as a compass
-fundamental property of some forms of matter

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32
Q

magnetism-

A

-magnetic oxide of iron
-naturally occurring & used as a compass
-fundamental property of some forms of matter
-fundamental form of nature (always existed)

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33
Q

any charged particle in motion creates-

A

magnetic field

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34
Q

magnetic field is-

A

-perpendicular to motion of the charged particle
-can be predicted in which way it’s going to go

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35
Q

magnetic fields-

A

are bipolar or dipolar
-indicates no matter what, wherever that field exists, both holes are represented
-have a north (positive) & south (negative) poles

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36
Q

magnetic dipole-

A

electrons rotating on their axis create a magnetic field

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37
Q

magnetic domain-

A

accumulation of these forms a magnetic domain

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38
Q

if all magnetic domains in an obj. are orientated the same way, then-

A

the object will act like a magnet

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39
Q

classification of magnets (4)-

A

-natural magnets
-artificially induced magnets
-electromagnets
-temporary magnets

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40
Q

natural magnets found-

A

in earth

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41
Q

artificially induced permanent magnet-

A

-usually iron
-non-magnetic materials placed in a strong magnetic field
-any item that has their domain aligned w: the field of an electromagnet

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42
Q

electromagnets ex-

A

wire wrapped around an iron core

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43
Q

temporary magnet-

A

artificially induced magnet

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44
Q

magnet classification of matter (6)-

A

-magnetic permeability
-non-magnetic
-diamagnetic
-paramagnetic
-ferromagnetic
-magnetic susceptibility

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45
Q

magnetic permeability-

A

ability to attract magnetic field lines

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46
Q

non magnetic-

A

unaffected by magnetic field

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47
Q

diamagnetic-

A

weakly repelled by both poles

48
Q

paramagnetic-

A

weakly attracted to both poles

49
Q

ferromagnetic-

A

strongly attracted by magnetic fields (most metals- soft irons)

50
Q

magnetic susceptibility-

A

ease at which materials can be changed into a magnet

51
Q

magnetic laws-

A

-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
Q

ferromagnetic material can be made into a magnet by-

A

induction

53
Q

if a material doesn’t retain magnetic property after removal from an external magnetic field, it is-

A

a temporary magnet

54
Q

low stone is-

A

naturally magnetic

55
Q

electromagnetism-

A

force associated w: electrons in motion

56
Q

fundamental forces of nature in electromagnetism-

A

-gravity
-strong nuclear force
-weak nuclear reaction

57
Q

electricity & magnetism are-

A

different aspects of the same force

58
Q

scientist believed electricity & magnetism were-

A

2 separate forces

59
Q

research was limited because-

A

electricity couldn’t be produced & controlled

60
Q

research was restricted to-

A

electrostatics

61
Q

method of producing flow of electrons stimulated investigations of-

A

electricity & magnetism

62
Q

Galvani discovered-

A

a frogs leg twitched when touched by 2 different metals (similar to electrostatic charge)

63
Q

Alessandro Volta-

A

used this to experiment w: other metals to induce an electric current

64
Q

voltic plates-

A

stacked zinc & copper plated & produced a weak electric current

65
Q

modern batteries used-

A

a carbon rod as a + electrode & a zinc cylindrical can (-) filled w: electrostatic paste

66
Q

source of EMF (Electromagnetic Force)

A

any device that converts energy directly into the electric energy

67
Q

Oersted’s Experiment-

A

-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
Q

if a charge is in motion, a magnetic field is-

A

induced

69
Q

right hand rule-

A

applies to solenoids

70
Q

solenoid-

A

coil of wire

71
Q

inside the loop of the coil of the magnetic field lines are-

A

concentrated

72
Q

,magnetic field lines of a solenoid are stronger-

A

inside the coil

73
Q

magnetic field can be further intensified by-

A

putting a ferromagnetic material inside the solenoid

74
Q

Faraday’s first law-

A

law of electromagnetic introduced

75
Q

if an electric current induces a magnetic field, then does a magnetic field induce an electric current?

A

no, it has to be in a changing magnetic field

76
Q

animeter-

A

measures amps

77
Q

changing magnetic field-

A

magnetic field that changes its intensity or direction

78
Q

the current magnitude depends on 4 things-

A

-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
Q

turns ratio-

A

number of turns in a conductor

80
Q

parallel circuits have the greatest-

A

magnitude/strength of currents

81
Q

changing magnetic fields can be produced 3 ways-

A

-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
Q

changing magnetic field ex-

A

radio reception

83
Q

changing magnetic fields can induce-

A

current (A/C current)

84
Q

Lenz’s law-

A

2nd law of electromagnetics

85
Q

lenz’s law determined-

A

how to tell the direction of induced current flow

86
Q

magnetic field induced-

A

opposes a field that induced it (in other words, north induces north)

87
Q

2 basic types of electromagnetic induction-

A

-self induction
-mutual induction

88
Q

self induction-

A

induction of an opposing magnetic field in a single coil by its own changing magnetic field

89
Q

mutual induction-

A

generation of an altering current in a secondary coil by supplying & alternating current to the primary coil

90
Q

only difference b/w self & mutual induction-

A

the number of solenoids

91
Q

electromagnetic devices-

A

-application derived from Oersted/s & Faraday’s experiments
-electric generator, electric motor, & transformer

92
Q

electromechanical devices is a practical use of-

A

mutual induction

93
Q

in an electric generator, mechanical energy is converted to-

A

electrical energy

94
Q

in an electric generator, mechanical energy can be supplied by-

A

hand, wind, water, & heat

95
Q

simple generators produce-

A

alternating current

96
Q

an electric generator w: a commuter ring-

A

A/C is changed to pulsating D/C

97
Q

electric motors convert electric energy to-

A

mechanical energy (rotation)

98
Q

current motor-

A

simple form

99
Q

induction motor used in most-

A

x-ray tubes

100
Q

rotators & stators-

A

both are solenoids

101
Q

stator electromagnets-

A

coils of wire that are stationary

102
Q

stationary rotators can-

A

can move

103
Q

the transformer-

A

transforms electric potential & current

104
Q

the transformer consists of-

A

solenoids w: ferromagnetic material in the center

105
Q

if ferromagnetic material is shaped like a magnetic field, then it is said to have-

A

good coupling

106
Q

job of the transformer-

A

transform voltage

107
Q

the transformer uses-

A

mutual induction

108
Q

voltage on the secondary/induced side of the transformer-

A

is directly proportional to the ratio of the number of turns of secondary coil to the number of turns in the primary side

109
Q

transformer law-

A

Vs/Vp = Ns/Np (Ns/Np is called turns ratio)

110
Q

step-up transformer-

A

-turns ratio greater than 1
-speeds up voltage
-current decreases

111
Q

step-down transformer-

A

-turns ratio less than 1
-top number smaller than bottom number
-slows down voltage
-current increases

112
Q

transformer inefficiency-

A

loss of efficiency is minimal

113
Q

3 main causes of efficiency loss in the transformer-

A

-resistance- due to heat & Ohm’s law
-hysteresis- due to changing magnetic field
-eddy currents- due to lenz’s law

114
Q

types of transformers (4)-

A

-autotransformer
-closed-core
-open-core
-shell-type

115
Q

autotransformer-

A

basically a transformer that has primary & secondary connections, but only has 1 solenoid

116
Q

closed-core-

A

more efficient than open-core

117
Q

shell-type-

A

most efficient type & most commonly used

Radt. 3011 (13 decks)

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