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Physics > Ch 4 Electricity, Magnetism & Electromagnestism > Flashcards

Ch 4 Electricity, Magnetism & Electromagnestism Flashcards

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1
Q

*electrostatics is:

A

the study of stationary electric charges

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2
Q

*matter has ____ and _______, matter may also have ____

A

mass and energy equivalence, may also have electric charge

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3
Q

being electrified means there is:

A

too few or too many electrons

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4
Q

*electrification can be created by:

A

contact, friction & induction

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5
Q

*unlike charges ___; like charges _____

A

attract; repel

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6
Q

the force of attraction b/w 2 unlike charges or the force of repulsion b/w 2 like charges is called ____

A

electrostatic force

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7
Q

*Coulomb’s law: the electrostatic force is directly proportional to ______ and inversely proportional to the ____

A

the product of the electrostatic charges; square of the distance b/w them

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8
Q

electrostatic force is very strong when ____ and rapidly decreases when ____

A

objects are close together; objects are separated

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9
Q

*electric charge distribution is:

A

uniform throughout or on the surface

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10
Q

*electric charge of a conductor is:

A

concentrated along the sharpest curvature of the surface

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11
Q

*the unit of electric potential is:

A

volt (V)

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12
Q

the higher the voltage the ____ the potential to do work

A

greater

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13
Q

if electric potential is applied to an object then:

A

electrons move along that object in an electric current or electricity

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14
Q

*electrodynamics is:

A

the study of electric charges in motion

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15
Q

the direction of electric current is always:

A

opposite that of electron flow

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16
Q

*a conductor is:

A

any substance in which electrons flow easily; metals, copper, water

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17
Q

*an insulator is:

A

any material that does not allow electron flow; glass, clay, earth like materials

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18
Q

semiconduction

A

demonstrated in 1946 by William Shockley, materials are Si silicon and Ge germanium, led to microchips and computer technology

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19
Q

*a semiconductor is:

A

any material that under come conditions acts as a conductor while under other conditions acts as an insulator

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20
Q

superconductivity

A

the property of some materials to exhibit no resistance below a critical temperature (Tc)

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21
Q

an electric circuit is when:

A

the resistance is controlled and the conductor is a closed path

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22
Q

*increasing electric resistance results in:

A

a reduced electric current

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23
Q

electric current is measured in ____

A

amperes (A)

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24
Q

an A is proportional to the:

A

number of electrons flowing in the electric circuit

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25
Q

1A=

A

1 electric charge flowing per second

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26
Q

electric resistance is measured in ____

A

ohms

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27
Q

*Ohm’s Law:

A

the voltage across a total circuit or any portion of the circuit is equal to the current times the resistance V=IR

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28
Q

*in a series circuit all circuit elements are:

A

connected in a line across the same conductor

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29
Q

*a parallel circuit contains elements that are:

A

connected at their ends rather than lying in a line across the conductor

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30
Q

*direct current (DC):

A

electrons can be made to flow one direction along the conductor

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31
Q

alternating current (AC)____, occurs____, is ___Hz

A

current where electrons oscillate back and forth, occur sinusoidally requiring 1/60 s, 60Hz current

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32
Q

DC is represented by:

A

a horizontal line

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33
Q

AC is represented by:

A

a sine curve, electrons flow positively first, then negatively

34
Q

*any charged particle in motion creates:

A

a magnetic field

35
Q

*the lines of a magnetic field are always:

A

closed loops

36
Q

lines of a magnetic field are _____ or _____ and always have a ___ and a ____

A

bipolar or dipolar; north and a south pole

37
Q

a magnetic dipole is:

A

the small magnet created by the electron orbit

38
Q

the accumulation of many atomic magnets with their dipoles aligned creates a:

A

magnetic domain

39
Q

*magnetic permeability is:

A

the ability of a material to attract the lines of magnetic field intensity

40
Q

3 principle types of magnets:

A

naturally occurring, artificially induced permanent magnets & electromagnets

41
Q

*magnets are classified according to:

A

the origin of their magnetic property

42
Q

electromagnets consist of:

A

wire wrapped around an iron core, when electric current flows through the wire a magnetic field is created

43
Q

*all matter can be classified according to:

A

the manner in which it interacts with an external magnetic field

44
Q

nonmagnetic

A

unaffected by a magnetic field, wood, glass

45
Q

diamagnetic

A

weakly repelled by both poles of the magnetic field, not attracted to a magnet, water, plastic

46
Q

paramagnetic

A

weakly attracted to both poles of a magnetic field, slightly attracted to a magnet, gadolinium, contrast agents

47
Q

ferromagnetic

A

can be permanently magnetized by exposure to a magnetic field, strongly attracted to a magnet, iron, nickel, cobalt

48
Q

like magnetic poles ____, unlike magnetic poles _____

A

repel, attract

49
Q

some materials can be made magnetic by:

A

induction

50
Q

imaginary magnetic fields are called _______, their density is ____

A

magnetic lines of induction, proportional to he intensity of the magnetic field

51
Q

*ferromagnetic objects can be made into magnets by:

A

induction

52
Q

*the magnetic force is proportional to the:

A

product of the magnetic pole strengths divided by the square of the distance between them

53
Q

*the SI unit of magnet field strength is the ___; an older unit is the ______; __T=______G

A

tesla; gauss; 1T=10,000G

54
Q

*electric potential is measured in units of ___

A

Joule per coulomb, or volt

55
Q

*any charge in motion:

A

induces a magnetic field

56
Q

a coil of wire is called a ____

A

solenoid

57
Q

*an electromagnet is:

A

a current carrying coil of wire wrapped around an iron core, which intensifies the induced magnetic field

58
Q

an ammeter is:

A

a current measuring device

59
Q

*electromagnetic induction:

A

an electric current is induced in a circuit if some part of that circuit is in a changing magnetic field

60
Q

*varying magnetic field intensity:

A

induces an electric current

61
Q

*an induction motor:

A

powers the rotating anode os an x-ray tube

62
Q

*a transformer:

A

changes the intensity of alternating voltage and current

63
Q

a transformer will operate only with:

A

a changing electric current (AC)

64
Q

step-up transformer:

A

has a turns ratio of greater than 1 b/c the voltage is increased from primary to secondary

65
Q

step-down transformer:

A

has a turns ratio of less than 1

66
Q

*an autotransformer has:

A

one winding and varies both voltage and current

67
Q

current and electron flow are always:

A

opposite

68
Q

the primary function of an x-ray imaging system is to:

A

convert electric energy into electromagnetic energy

69
Q

in induction only ____ charges move

A

negative

70
Q

in a transformer if the voltage goes up the current goes ___

A

down

71
Q

examples of a small resistance:

A

a large diameter or a small distance

72
Q

in a diode electrons flow:

A

in one direction

73
Q

superconductors (do/dont) follow ohm’s law?

A

DON’T

74
Q

electric and magnetic field lines are always _____

A

perpendicular

75
Q

a photons frequency, wavelength & energy can _____, but a photon will always travel _____

A

vary, at the speed of light

76
Q

a motor is ____ energy

A

mechanical

77
Q

a generator is ____ energy

A

electric

78
Q

the ground is where everything _____, the earth has ____ charges

A

neutralizes, negative

79
Q

2 coils is _____; 1 coil is _____

A

mutual induction; self induction

80
Q

in the domain magnets run:

A

south to north

81
Q

the magnetic field runs:

A

north to south

82
Q

the domain is ___ the magnet

A

within

Physics (13 decks)

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