# physics y9 Flashcards

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1
Q

ammeter

A

used to measure current;
connected in series;
low resistance to allow current to pass through

2
Q

ampere

A

the unit of current (A)

1A = 1C/s

3
Q

atom

A

smallest unit of ordinary matter, has equal electrons and protons

4
Q

cause of static electricity

A

friction from two insulators,
removes electrons from one object and deposits them on the surface of the other object
the electrons build up on the surface because electricity cannot pass through the objects

5
Q

charged particle

A

particle with an electric charge, e.g. ion, electron, proton

6
Q

circuit

A

a loop of wire which connects an energy source to an energy user

7
Q

conductor

A

materials that electricity can flow through (the material is conducted);
electrons are held loosely by atoms and are freely able to move
water is non-conductive until an ion is added

8
Q

coulomb

A

the unit of elementary electrical charge
1C = 6.24 x 10^18 elementary charges
1C/second = 1A

9
Q

current

A

the rate of coulombs flowing in the circuit per second / the rate of flow of charge;
carried by electrons in a wire;
unit of current: amperes, unit A

10
Q

electricity

A

energy that is being transported between points;
the flow of electrons/negative charge
transported to be transformed into other energy types

11
Q

electricity, transfer

A

caused by moving of matter;
moving electrons transfer energy from energy source to energy user;
electron flow = kinetic energy

12
Q

electron

A

negatively charged, found in an electron cloud surrounding the atom, extremely small

13
Q

elementary charge

A

the fundamental unit of the size of the charge on one electron/one proton, symbol e
(proton = +e, electron = -e)

14
Q

energy

A

the ability of an object to do work;
when an object is making something happen, it is doing work;
work results from a force applied that causes displacement of the object;
can be transformed (to different forms of energy) and transferred (to different objects)

15
Q

energy source

A

an object that provides energy to the circuit, e.g. battery, generator
energy allows the electrons (that are already in the circuit) to move around

16
Q

energy transfer

A

energy being transferred between objects,

transferred by movement of matter or by wave motion between two places

17
Q

energy transformation

A

energy being converted to another energy form

18
Q

energy user

A

an object that needs the energy from an energy source, e.g. lightbulb, motor

19
Q

heat, transfer

A

refers to thermal energy being transferred from a hotter system to a cooler one

20
Q

insulator

A

materials that electricity cannot flow through (the material is insulated) OR materials of high resistance to the flow of current
electrons (-) are bound tightly to the atom (+)

21
Q

ion

A

atoms that gain/lose electrons

22
Q

kinetic energy, transfer

A

energy associated with motion;
caused by movement of matter,
transfer of kinetic energy,
transferred from one moving object to a stationery object via work

23
Q

light, transfer

A

light behaves as both a wave and a particle;

the wave model explains how light moves/travels + how it interacts with objects at macroscopic scales

24
Q

measuring resistance

A

achieved by finding current and voltage in a circuit and applying Ohm’s law

25
Q

mechanical waves

A

those requiring a medium (matter) to transport energy from one location to another (cannot transmit/propagate in a vacuum)
classified as longitudinal or transverse waves

26
Q

neutron

A

neutal/no charge, found in the nucleus of an atom, same size as a proton

27
Q

ohm’s law

A

the law that states that voltage and current are directly proportional if resistance remains constant
(V = IR) (I = V/R) (R = V/I)

28
Q

ohms law, current and resistance

A

current is inversely proportional to resistance

29
Q

ohms law, current and voltage

A

voltage of a circuit is directly proportional to the current of the circuit

30
Q

ohms law, voltage and resistance

A

voltage is directly proportional to resistance

• high voltage caused by high resistance
• low voltage caused by low resistance
31
Q

parallel circuit

A

a circuit with components arranged in branches (each branch has at least one component), branches do not depend on each other

32
Q

parallel circuit, current

A

branches with same resistance = same current throughout;
branches with different resistance = less resistance over greater current
total current is shared over all the branches

33
Q

parallel circuit, resistance

A

total resistance is always less than any of the branch resistances;
adding more parallel branches causes total resistance of a circuit to decrease (as there are more paths for current to choose from);
1/R1 + 1/R2 + 1/R3 = 1/R total

34
Q

parallel circuit, voltage

A

voltage across each component will be the same no matter what;
voltage is not affected by resistance

35
Q

potential difference/voltage

A

difference in potential energy across an energy source/circuit component, the ‘push’ of the current;
unit of potential energy: volts, V

36
Q

proton

A

positively charged particle, found in the nucleus of an atom, same size as an electron

37
Q

resistance

A

a measure of how difficult it is for current to flow through particular material;
unit of resistance: ohm (Ω)

38
Q

resistance in a circuit

A

resistance comes from circuit components; how much that component opposes the flow of current through it

39
Q

series circuit

A

when a circuit has components connected one after another in a continuous loop
all components are dependant on each other (will break if one component does not work)

40
Q

series circuit, current

A

same amount of current flows in every part of the circuit;
all electrons experience the same resistance;
the current measured at any point of the series circuit will be the same value

41
Q

series circuit, resistance

A

total resistance is equal to the sum of the individual resistor values
resistance increases as more components/resistors are added
R1 + R2 + R3 = RT

42
Q

series circuit, voltage

A

voltage may not be the same all around a series circuit,
larger voltage over components with larger resistance;
all voltage across a circuit adds up to the voltage supplied by the energy source

43
Q

sound, transfer

A

caused by wave motion;
sound is a form of kinetic energy;
speakers vibrate back and forth when they produce music;
as they move forward, they push on the nearest air particle (which pushes on the next particle and so on)
as they move backward, they pull the nearest particle back (next particle and so on)

44
Q

static discharge

A

occurs when there is a loss of static electricity due to;

• friction (rubbing)
• conduction (direct contact)
• induction (electrical field)
45
Q

static electricity

A
a type of electricity caused by a build up of charge, which is released when electrons are able to flow into another object
potential energy (does not move, is stored)
46
Q

temperature

A

used as a measure of degree of “hotness” and “coldness” of an object

47
Q

thermal energy, transfer

A

internal energy of a system due to its temperature;
caused by movement of matter,
temp increases because molecules of a substance move faster and gain thermal energy through heat transfer

thermal energy transfers occur through conduction, convention and radiation

48
Q

variable resistor

A

a resistor with an adjustable electric resistance value

49
Q

voltage in a circuit

A

provides energy to the circuit,
electrical potential energy is transformed into other energy types at circuit components (the potential energy is lost),

THE AMOUNT OF VOLTAGE GOING INTO THE CIRCUIT WILL BE DIFFERENT TO THE VOLTAGE LEAVING BECAUSE ENERGY IS TRANSFORMED (end voltage = 0V)

50
Q

voltmeter

A

measures voltage;
connects in parallel over a circuit component;
high resistance

51
Q

wave motion

A

activity that carries energy from one place to another through a medium without actually moving any matter;
a transfer of energy; has no net movement of matter

52
Q

transverse wave

A
• motion of the individual particles in the medium is perpendicular to the motion of the wave
• both the crest and trough of a wave are points of maximum displacement of the particles (mass) in the medium
53
Q

longitudinal wave

A
• motion of the individual particles in the medium is parallel to the motion of the wave;
• if the longitudinal wave moves left to right (and the energy flows left to right), then the individual particles in the medium vibrate left to right
• these particles do not travel down the length of the wave
• a longitudinal wave propagates by changing the pressure of the medium
54
Q

crest

A

particles are at the top of their upward motion;

found in transverse waves

55
Q

trough

A

particles are at the bottom of their downward motion;

found in transverse waves

56
Q

compression

A

region where many particles come together and there is higher than normal pressure;
found in longitudinal waves

57
Q

rarefaction

A

region where many particles are spread apart and there is lower than normal;
found in longitudinal waves

58
Q

amplitude

A

unit = (A)
the maximum displacement of a particle from its resting position
the greater the amplitude, the more energy/power it carries

59
Q

wave graph, displacement/distance

A

shows displacement of all particles, from undisturbed/resting positions, along the length of the wave at a particular point in time
x-axis = distance from source of the wave
y-axis = displacement of particles

60
Q

wavelength

A

unit = (λ)
the distance between two successive corresponding positions in a wave;
sometimes referred to as one cycle in the wave

61
Q

wave graph, displacement/time

A

A displacement-time graph follows the motion of an individual particle in the wave and shows its displacement from its resting position over time

62
Q

period

A

the time it takes to complete one cycle (wavelength) of the wave
unit = (T)

63
Q

properties of waves

A

amplitude, frequency, wavelength, period

64
Q

frequency

A

the number of wavelengths passing any given point each second
unit = (f)
measured in hertz (Hz)
1 Hz = 1 wavelength passing each second

65
Q

frequency and period

A

frequency is inverse of period; increase in frequency results in reduced period and vice verse

𝑇=1⁄𝑓 𝑎𝑛𝑑 𝑓=1⁄𝑇

66
Q

wave speed

A

the rate at which the wave covers distance
unit = m/s
speed of a wave remains constant while travelling in the same medium
(speed = distance/time)

67
Q

wave equations

A
v = f x λ
T = 1/f AND f = 1/T
distance = speed x time
68
Q

wave energy, communication

A

electromagnetic waves- transmits digital signals from your phone to a base station
microwave/radio signals- sends phone call from base station to the person you are calling

69
Q

electromagnetic waves

A

EM waves transfer energy via electrical and magnetic disturbances;
transverse waves, no medium required;
all electromagnetic waves travel at the speed of light BUT may slow down in other media/matter

70
Q

electromagnetic spectrum

A

different types of electromagnetic waves form the electromagnetic spectrum;

the higher the frequency (therefore shorter wavelength), the more dangerous the wave is

71
Q

all waves on the electromagnetic spectrum

A
2. microwaves
3. infrared
4. visible light
5. ultra violet
6. x-ray
7. gamma
72
Q

A

longest wavelength, lowest frequency, least intense
can be short as a football, long as a football field

e.g. tv signals, cellphone signal, radio signal

73
Q

microwaves

A
wavelengths measured in cm;
long wavelength (not as long as radio waves) + low frequency, low intensity

microwaves energy penetrates haze, light, rain, snow, clouds and smoke;
makes it good for transmitting

e.g. wifi, gps, ovens, communication systems

74
Q

A

wavelengths of around 700nm (nanometers) to 1mm
moderately long wavelength (shorter than microwaves, longer than visible light), low frequency, moderately low intensity

e.g. tv remote control, sunlight heat, fire, radiator

75
Q

visible light

A

around 400-700nm wavelength;
moderate wavelength, frequency and intensity;

made up of various frequencies of coloured light;
the colour is determined by the frequency of light;

(lowest frequency = purple / highest frequency = red)

when EM radiation of this frequency falls on out retina, our brain interprets it as colour

76
Q

ultraviolet light

A

100-400nm wavelengths;
moderately short wavelength, moderately high frequency, moderate-high intensity

higher frequency than visible light
e.g. used for killing bacteria, security coding

77
Q

x-rays

A

short wavelength, high frequency, high intensity
0.01-10nm wavelength;
x-ray radiation has a high penetration ability, can pass through our bodies;
over exposure can cause tissue damage
e.g. x-ray scans, mammograms (x-ray for breast cancer)

78
Q

gamma rays

A

shortest wavelength, highest frequency, highest intensity;

generated by radioactive atoms and in nuclear explosions;
can kill living cells

e.g. radiotherapy (medicine), sterilisation and disinfection

79
Q

reflection

A

when light bounces off an object

80
Q

specular reflection

A

when light reflects off a smooth and shiny surface;
the light will reflect at the same angle as it hit the surface;
angle of incidence = angle of reflection

81
Q

diffuse reflection

A

when light hits a rough object and reflects in lots of different directions

82
Q

angle of reflection

A

angle at which light bounces off a reflecting surface

83
Q

concave mirror

A

light rays travelling in a straight line towards the mirror are reflected inwards; the rays meet at a focal point
makes thing appear larger (useful for applying makeup)
(light reflecting off curved mirror)

84
Q

angle of incidence

A

angle at which light hits a reflecting surface

85
Q

convex mirror

A

light rays travelling in a straight line towards the mirror are reflected outwards;
gives a wider field of vision, useful for rear view mirrors in cars + mirrors in corners
(light reflecting off curved mirrors)

86
Q

absorption

A

transfer of light energy into an object; instead of bouncing off an object’s surface, a light ray might be absorbed

87
Q

transmission

A

light ray passing through an object without being absorbed

88
Q

speed of light

A

the speed at which light and all forms of electromagnetic waves travel in a vacuum;
light waves move at different speeds for each medium, but it is always slower than in a vacuum;
formula = 3 × 10^8 m/s

89
Q

refraction

A

the bending of light as it passes from one material into another;;

light always travels at the same speed in the air
when light passes from air into water or glass (a matter with a different density), it slows down slightly and changes direction

90
Q

sound waves

A

longitudinal wave energy transfer (cannot travel through a vacuum)

91
Q

speed of sound

A

330m/s
sound travels faster in hot air than cold air, does not depend on air pressure;
moves through different materials at different speeds

92
Q

echoes

A

sound reflected from hard surfaces,

e.g. sonar, echo sounding, ultrasound

93
Q

sonar

A

uses echoes to map/locate objects in surrounding environment

1. emit a cluster of sound waves in the direction of an object 2. while a few waves will bounce off it, the remaining waves will be reflected back in the direction of the emitter
94
Q

sound absorption

A

soft materials absorb sound and turn it into heat

95
Q

loudness

A

sound loudness depends on the amplitude of wave
(amplitude = how much energy in the wave)
big amplitude = big sound

96
Q

pitch

A

pitch depends on how many vibrations there are;
more frequent vibrations (higher frequency) = higher pitch
the more frequency means waves are squished (shorter wavelength)
the higher the pitch, the higher the frequency, the shorter the wavelength

97
Q

ultrasound

A

sound waves with frequencies that are above human hearing range (more than 20,000Hz),
used for cleaning things and scanning pregnancy

98
Q

hearing thresholds (human + animals)

A

your ability to hear reduces as you age;
young people hear in a frequency range up to 20000Hz;
people over 65 can only hear in a frequency range of around 5000Hz
dogs and cats hear sound frequencies outside human hearing thresholds

99
Q

infrasound

A

sound waves with frequencies that are below human hearing range (less than 20Hz)

100
Q

outer ear

A

pinna/auricle + ear canal

101
Q

middle ear

A

ear drum + ossicles + eustachian tube

102
Q

inner ear

A

vibrations from the ossicles enter the cochlea\

contains the cochlea

103
Q

pinna/auricle

A

outer ear; the visible part of the ear, collects sound waves

104
Q

ear canal

A

outer ear; a passage comprised of bone and skin that leads to the eardrum

105
Q

ear drum

A

middle ear; sound waves cause the ear drum to vibrate, the vibrations are transferred to the ossicles

106
Q

ossicles

A

contains the three smallest bones in your body

• malleus, hammer
• incus, anvil
• stapes (stirrup), the smallest bone in the body
107
Q

eustachian tube

A

middle ear; protects, aerates, and drains fluid from the middle ear + permits the gas pressure in the middle ear cavity to adjust to external air pressure

108
Q

cochlea

A

inner ear;
a snail like tube; filled with liquid that moves like a wave from the vibrations, has tiny cells covered in microscopic hairs (cilia) that move;
creates nerve signals that goes to the brain that turns it into sound

109
Q

auditory nerve

A

inner ear; carries neural signals from the cochlea to the brain for interpretation