physics Flashcards
1
Q
what does negatively charged mean?
A
more electrons than protons
2
Q
what does positively charged mean?
A
less electrons than protons
3
Q
can electrons transfer?
A
yes
4
Q
can protons transfer?
A
no
5
Q
what kind of charges repel?
A
like charges
6
Q
what kind of charges attract?
A
opposite charges
7
Q
what is the unit of charge?
A
coulomb (C)
8
Q
what are conductors?
A
an object that allows electrons to move through freely (conducts electric current)
9
Q
what are insulators?
A
objects that do not conduct electric current
10
Q
what is a field?
A
a region of influence around a source
11
Q
what is a test body?
A
an observable object that experiences a force due to the field
12
Q
what is a gravitational field?
A
surrounds an object that has mass and exerts force on other objects with mass
13
Q
what is an electrical field?
A
surrounds an object that has charge and exerts force on other objects with charge
14
Q
what is a magnetic field?
A
surrounds a magnet and exerts force on other magnets and metals
15
Q
what are vectors?
A
- gravitational field
- electrical field
- magnetic field
16
Q
what is field strength?
A
the strength of a field on a test body
17
Q
what is the effect of distance on field strength?
A
field strength decreases as distance from the source increases
18
Q
what are field lines?
A
used to describe the direction of the field and the strength – the denser the field lines, the stronger the field
19
Q
what is the direction of force in a gravitational field?
A
towards the centre of the source
20
Q
how are electrical fields created?
A
created when electrons are transferred
21
Q
what is the direction of force in an electrical field and magnetic field?
A
the direction of force follows the electrons
22
Q
what is an electric current?
A
a flow of electric charge from one point to another
23
Q
what are all magnetic fields generated by?
A
moving charges
24
Q
why do most magnetic fields end up cancelling out?
A
because the electrons don’t align
25
what produces a permanent magnet?
when it is impossible to align the atoms so the fields line up and reinforce each other
26
what does a motor do?
changes electrical energy into mechanical energy
27
what does a generator do?
changes mechanical energy into electrical energy
28
what is an armature?
an electromagnet (a coil of wire around a piece of metal)
29
what is a commutator?
site of electron transfer
30
what is a shaft?
the rotating axis
31
what is a brush?
make contact with the commentator for transfer of electric current
32
what is a field magnet
a permanent magnet
33
what are the two types of power current?
1. alternating current
| 2. direct current
34
what is electromagnetic induction?
production of electrical energy in a conductor as a result of a moving magnetic field
35
what are responsible for flipping the electric field in a motor?
the commutator and the brushes
36
what is direct current?
a flow of charges that does not increase or decrease and flows in a single direction
37
what is an alternating current?
a flow of charges that reverses direction at regular intervals
38
what type of commutator does a DC require?
a split ring commutator (has gaps)
39
what type of commutator does an AC require?
a slip ring commutator (no gaps)
40
what is a circuit?
a closed loop for moving charges
41
what is a series circuit?
a single path for electrical current -- charges have to flow through one device before passing onto the next
42
what is a parallel circuit?
more than one path available -- current divides allowing the current to pass through different devices at the same time
43
what is voltage?
the electric potential difference between two points
44
what is resistance?
opposition to the passage of current through a conductor
45
how is heat generated?
through friction between electrons
46
what does resistance depend on?
the length, thickness and type of wire
47
what does electric current depend on?
the number of electrons that pass a point in a circuit every second
48
what is current measured in?
amps
49
what is electromotive force?
the force required to make the current flow
50
what value stays constant in a series circuit?
current
51
what value stays constant in a parallel circuit?
voltage
52
what is power?
the rate at which energy is used
53
what is power directly related to?
current and voltage
54
what is a multimeter?
a device used to measure quantities in a circuit
55
what must you do before measuring any quantity?
make sure the dial is set to measure the desired quantity
56
to measure what quantity does a multimeter have to be set up in series?
to measure current
57
to measure what quantity does a multimeter have to be set up in parallel?
to measure voltage
58
why is there large potential for power loss in electricity distribution?
because current must flow through kilometres of wire
59
what are transformers?
devices that transform AC voltage from low to high or vice versa
60
what are the three main parts of a transformer?
1. soft iron core
2. primary coil
3. secondary coil
61
what is the primary coil of a transformer?
connected to the input energy
62
what is the secondary coil of a transformer?
connected to the device (outputs energy)
63
what are the two types of transformers?
1. step up
| 2. step down
64
what is a step up transformer?
the secondary coil is wrapped more times than the primary so the voltage is increased
65
what is a step down transformer?
secondary coil is wrapped less times than the primary so the voltage is decreased
66
what are the characteristics of AC?
- high voltage
- low amperage
- less energy lost as heat
67
who created AC?
Tesla
68
who created DC?
Edison
69
what are the characteristics of DC?
- low voltage
- high amperage
- more energy lost as heat
70
what are the advantages of AC?
- can travel long distances without significant power loss
| - can be easily changed into higher or lower voltage
71
what are the advantages of DC?
- ideal for small appliances that need portability
- can be used as backup power
- lower voltage --> safer
72
what type of current can transformers be used on?
alternating current
73
what are the disadvantages of AC?
greater risk of electrocution due to high voltage
74
what are the disadvantages of DC?
- most effective when the source is connected to appliance
| - less effective over long distances
75
what is the electric field of AC?
direction of current alternates
76
what is the electric field of DC?
direction of current stays the same
77
what four devices are used to increase safety when using electrical energy?
1. circuit fuses
2. polarized plugs
3. breakers
4. ground wiring
78
what is a circuit fuse?
a safety device that protects electrical circuits from over current; it has a metal wire/strip that melts when too much current flows through it
79
what are polarized plugs?
there are both neutral and hot wires and a directional flow to how the current runs through the system
80
what are breakers?
an electrical switch that will interrupt current flow after detection of a fault
81
what is ground wiring?
a wire acting as a conductor from an electric circuit to a ground
82
what is electromagnetic radiation?
a changing electric field and a changing magnetic field travelling at right angles to each other
83
what is EMR emitted from?
the stars (eg. the sun)
84
in what shape does EMR travel in?
waves
85
what are transverse waves?
the vibrations are perpendicular to the direction the wave travels
86
what is frequency?
how often a cycle occurs per second
87
what is frequency measured in?
hertz (Hz)
88
what are characteristics of high frequency?
- short wave lengths
- more dangerous
- ionizing radiation
89
what are characteristics of low frequency?
- long wave length
- less dangerous
- non-ionizing
90
what are photons?
bundles of light energy that move at the speed of light
91
what do solar flares from the sun emit?
xrays, gamma rays and radio waves
92
who proposed the photon theory?
einstein
93
what is refraction?
the bending of a wave due to a change in speed
94
what is reflection?
the return of a wave from a surface
95
what is polarization?
confining a wave to vibrate in one direction
96
what is diffraction?
the bending of a wave as it passes by a boundary or object
97
what is a normal line?
a line drawn perpendicular to the surface of the mirror or boundary where refraction of reflection occurs
98
what happens as a light ray goes from a less dense to a more dense substance?
the light bends toward the normal line
99
what does the amount of bending in a refraction depend on?
the density if the substance
100
what is the angle of incidence?
the angle between an incoming light ray and the normal line
101
what is the angle of reflection?
the angle between the reflected light ray and the normal line
102
what is unpolarized light?
electromagnetic waves that are vibrating in many different planes
103
what is polarized light?
filtered light that only vibrates in one plane
104
what does the amount of bending in diffraction depend on?
the size of the opening
105
what does a wide gap create?
high resolution image
106
what does a narrow gap create?
low resolution image
107
who created the refracting telescope?
galileo
108
what type of lenses does a refracting telescope use?
convex and concave lenses
109
who created the reflecting telescope?
newton
110
what type of lenses does a reflecting telescope use?
a convex lens, plane and concave mirror
111
what are radiation telescopes?
they use satellites to collect data on all types of EMR, don't work well with high frequency
112
what forms EMR?
thermonuclear fusion
113
what is thermonuclear fusion?
when two hydrogen atoms combine to form a helium atom and one neutron (H + H --> He + n)
114
why are stars so hot?
because thermonuclear fusion releases so much energy
115
what forms gamma rays?
the nuclear fusion reaction
116
where do gamma rays come from?
the sun's core
117
how does a spectroscope work?
the light from stars is passed through a prism or diffraction grating and separated into its component wavelengths
118
what are the 3 types of spectra?
1. continuous spectrum
2. dark line/absorption line spectrum
3. bright line/emission line spectrum
119
what is a continuous spectrum?
all colours of the spectrum are emitted
120
what is dark line/absorption line spectrum?
spectrum with a series of dark lines, each gas has its own unique absorption spectrum which can be used to identify gases
121
what is bright line/emission line spectrum?
a black background with coloured bands of light, produced when energy is passed through a gas, the gas absorbs specific wavelengths of energy and that energy is emitted as photons of light at specific wavelengths which gives them specific color
122
what is the doppler effect?
a change in the observed frequency of a wave due to motion between the source and the observer
123
when does a star collapse?
when the fuel is used up and the energy flow from the energy flow from the star's core stops
124
what is the evolution of a low mass star?
nebulae, low mass star, red giant, planetary nebula, white dwarf
125
what is the evolution of an intermediate mass star?
nebulae, intermediate mass star, supergiant, supernova, neutron star
126
what is the evolution of a high mass star?
nebulae, high mass star, supergiant, star collapse supernova, blackhole
