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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
1A=
1 electric charge flowing per second
26
electric resistance is measured in ____
ohms
27
*Ohm's Law:
the voltage across a total circuit or any portion of the circuit is equal to the current times the resistance V=IR
28
*in a series circuit all circuit elements are:
connected in a line across the same conductor
29
*a parallel circuit contains elements that are:
connected at their ends rather than lying in a line across the conductor
30
*direct current (DC):
electrons can be made to flow one direction along the conductor
31
alternating current (AC)____, occurs____, is ___Hz
current where electrons oscillate back and forth, occur sinusoidally requiring 1/60 s, 60Hz current
32
DC is represented by:
a horizontal line
33
AC is represented by:
a sine curve, electrons flow positively first, then negatively
34
*any charged particle in motion creates:
a magnetic field
35
*the lines of a magnetic field are always:
closed loops
36
lines of a magnetic field are _____ or _____ and always have a ___ and a ____
bipolar or dipolar; north and a south pole
37
a magnetic dipole is:
the small magnet created by the electron orbit
38
the accumulation of many atomic magnets with their dipoles aligned creates a:
magnetic domain
39
*magnetic permeability is:
the ability of a material to attract the lines of magnetic field intensity
40
3 principle types of magnets:
naturally occurring, artificially induced permanent magnets & electromagnets
41
*magnets are classified according to:
the origin of their magnetic property
42
electromagnets consist of:
wire wrapped around an iron core, when electric current flows through the wire a magnetic field is created
43
*all matter can be classified according to:
the manner in which it interacts with an external magnetic field
44
nonmagnetic
unaffected by a magnetic field, wood, glass
45
diamagnetic
weakly repelled by both poles of the magnetic field, not attracted to a magnet, water, plastic
46
paramagnetic
weakly attracted to both poles of a magnetic field, slightly attracted to a magnet, gadolinium, contrast agents
47
ferromagnetic
can be permanently magnetized by exposure to a magnetic field, strongly attracted to a magnet, iron, nickel, cobalt
48
like magnetic poles ____, unlike magnetic poles _____
repel, attract
49
some materials can be made magnetic by:
induction
50
imaginary magnetic fields are called _______, their density is ____
magnetic lines of induction, proportional to he intensity of the magnetic field
51
*ferromagnetic objects can be made into magnets by:
induction
52
*the magnetic force is proportional to the:
product of the magnetic pole strengths divided by the square of the distance between them
53
*the SI unit of magnet field strength is the ___; an older unit is the ______; __T=______G
tesla; gauss; 1T=10,000G
54
*electric potential is measured in units of ___
Joule per coulomb, or volt
55
*any charge in motion:
induces a magnetic field
56
a coil of wire is called a ____
solenoid
57
*an electromagnet is:
a current carrying coil of wire wrapped around an iron core, which intensifies the induced magnetic field
58
an ammeter is:
a current measuring device
59
*electromagnetic induction:
an electric current is induced in a circuit if some part of that circuit is in a changing magnetic field
60
*varying magnetic field intensity:
induces an electric current
61
*an induction motor:
powers the rotating anode os an x-ray tube
62
*a transformer:
changes the intensity of alternating voltage and current
63
a transformer will operate only with:
a changing electric current (AC)
64
step-up transformer:
has a turns ratio of greater than 1 b/c the voltage is increased from primary to secondary
65
step-down transformer:
has a turns ratio of less than 1
66
*an autotransformer has:
one winding and varies both voltage and current
67
current and electron flow are always:
opposite
68
the primary function of an x-ray imaging system is to:
convert electric energy into electromagnetic energy
69
in induction only ____ charges move
negative
70
in a transformer if the voltage goes up the current goes ___
down
71
examples of a small resistance:
a large diameter or a small distance
72
in a diode electrons flow:
in one direction
73
superconductors (do/dont) follow ohm's law?
DON'T
74
electric and magnetic field lines are always _____
perpendicular
75
a photons frequency, wavelength & energy can _____, but a photon will always travel _____
vary, at the speed of light
76
a motor is ____ energy
mechanical
77
a generator is ____ energy
electric
78
the ground is where everything _____, the earth has ____ charges
neutralizes, negative
79
2 coils is _____; 1 coil is _____
mutual induction; self induction
80
in the domain magnets run:
south to north
81
the magnetic field runs:
north to south
82
the domain is ___ the magnet
within

Physics (13 decks)

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