physics y9 Flashcards
ammeter
used to measure current;
connected in series;
low resistance to allow current to pass through
ampere
the unit of current (A)
1A = 1C/s
atom
smallest unit of ordinary matter, has equal electrons and protons
cause of static electricity
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
charged particle
particle with an electric charge, e.g. ion, electron, proton
circuit
a loop of wire which connects an energy source to an energy user
conductor
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
coulomb
the unit of elementary electrical charge
1C = 6.24 x 10^18 elementary charges
1C/second = 1A
current
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
electricity
energy that is being transported between points;
the flow of electrons/negative charge
transported to be transformed into other energy types
electricity, transfer
caused by moving of matter;
moving electrons transfer energy from energy source to energy user;
electron flow = kinetic energy
electron
negatively charged, found in an electron cloud surrounding the atom, extremely small
elementary charge
the fundamental unit of the size of the charge on one electron/one proton, symbol e
(proton = +e, electron = -e)
energy
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)
energy source
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
energy transfer
energy being transferred between objects,
transferred by movement of matter or by wave motion between two places
energy transformation
energy being converted to another energy form
energy user
an object that needs the energy from an energy source, e.g. lightbulb, motor
heat, transfer
refers to thermal energy being transferred from a hotter system to a cooler one
transferred through conduction, convection, radiation
insulator
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 (+)
ion
atoms that gain/lose electrons
kinetic energy, transfer
energy associated with motion;
caused by movement of matter,
transfer of kinetic energy,
transferred from one moving object to a stationery object via work
light, transfer
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
measuring resistance
achieved by finding current and voltage in a circuit and applying Ohm’s law
mechanical waves
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
neutron
neutal/no charge, found in the nucleus of an atom, same size as a proton
ohm’s law
the law that states that voltage and current are directly proportional if resistance remains constant
(V = IR) (I = V/R) (R = V/I)
ohms law, current and resistance
current is inversely proportional to resistance
ohms law, current and voltage
voltage of a circuit is directly proportional to the current of the circuit
ohms law, voltage and resistance
voltage is directly proportional to resistance
- high voltage caused by high resistance
- low voltage caused by low resistance
parallel circuit
a circuit with components arranged in branches (each branch has at least one component), branches do not depend on each other
parallel circuit, current
branches with same resistance = same current throughout;
branches with different resistance = less resistance over greater current
total current is shared over all the branches
parallel circuit, resistance
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
parallel circuit, voltage
voltage across each component will be the same no matter what;
voltage is not affected by resistance
potential difference/voltage
difference in potential energy across an energy source/circuit component, the ‘push’ of the current;
unit of potential energy: volts, V
proton
positively charged particle, found in the nucleus of an atom, same size as an electron
resistance
a measure of how difficult it is for current to flow through particular material;
unit of resistance: ohm (Ω)
resistance in a circuit
resistance comes from circuit components; how much that component opposes the flow of current through it
series circuit
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)
series circuit, current
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
series circuit, resistance
total resistance is equal to the sum of the individual resistor values
resistance increases as more components/resistors are added
R1 + R2 + R3 = RT
series circuit, voltage
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
sound, transfer
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)
static discharge
occurs when there is a loss of static electricity due to;
- friction (rubbing)
- conduction (direct contact)
- induction (electrical field)
static electricity
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)
temperature
used as a measure of degree of “hotness” and “coldness” of an object
thermal energy, transfer
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
variable resistor
a resistor with an adjustable electric resistance value
voltage in a circuit
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)
voltmeter
measures voltage;
connects in parallel over a circuit component;
high resistance
wave motion
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
transverse wave
- 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
longitudinal wave
- 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
crest
particles are at the top of their upward motion;
found in transverse waves
trough
particles are at the bottom of their downward motion;
found in transverse waves
compression
region where many particles come together and there is higher than normal pressure;
found in longitudinal waves
rarefaction
region where many particles are spread apart and there is lower than normal;
found in longitudinal waves
amplitude
unit = (A)
the maximum displacement of a particle from its resting position
the greater the amplitude, the more energy/power it carries
wave graph, displacement/distance
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
wavelength
unit = (λ)
the distance between two successive corresponding positions in a wave;
sometimes referred to as one cycle in the wave
wave graph, displacement/time
A displacement-time graph follows the motion of an individual particle in the wave and shows its displacement from its resting position over time
period
the time it takes to complete one cycle (wavelength) of the wave
unit = (T)
properties of waves
amplitude, frequency, wavelength, period
frequency
the number of wavelengths passing any given point each second
unit = (f)
measured in hertz (Hz)
1 Hz = 1 wavelength passing each second
frequency and period
frequency is inverse of period; increase in frequency results in reduced period and vice verse
𝑇=1⁄𝑓 𝑎𝑛𝑑 𝑓=1⁄𝑇
wave speed
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)
wave equations
v = f x λ T = 1/f AND f = 1/T distance = speed x time
wave energy, communication
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
electromagnetic waves
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
electromagnetic spectrum
different types of electromagnetic waves form the electromagnetic spectrum;
the higher the frequency (therefore shorter wavelength), the more dangerous the wave is
all waves on the electromagnetic spectrum
- radio waves
- microwaves
- infrared
- visible light
- ultra violet
- x-ray
- gamma
radio waves
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
microwaves
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
infrared radiation
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
visible light
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
ultraviolet light
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
x-rays
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)
gamma rays
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
reflection
when light bounces off an object
specular reflection
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
diffuse reflection
when light hits a rough object and reflects in lots of different directions
angle of reflection
angle at which light bounces off a reflecting surface
concave mirror
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)
angle of incidence
angle at which light hits a reflecting surface
convex mirror
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)
absorption
transfer of light energy into an object; instead of bouncing off an object’s surface, a light ray might be absorbed
transmission
light ray passing through an object without being absorbed
speed of light
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
refraction
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
sound waves
longitudinal wave energy transfer (cannot travel through a vacuum)
speed of sound
330m/s
sound travels faster in hot air than cold air, does not depend on air pressure;
moves through different materials at different speeds
echoes
sound reflected from hard surfaces,
e.g. sonar, echo sounding, ultrasound
sonar
(sound navigation and ranging)
uses echoes to map/locate objects in surrounding environment
- 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
sound absorption
soft materials absorb sound and turn it into heat
loudness
sound loudness depends on the amplitude of wave
(amplitude = how much energy in the wave)
big amplitude = big sound
pitch
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
ultrasound
sound waves with frequencies that are above human hearing range (more than 20,000Hz),
used for cleaning things and scanning pregnancy
hearing thresholds (human + animals)
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
infrasound
sound waves with frequencies that are below human hearing range (less than 20Hz)
outer ear
pinna/auricle + ear canal
middle ear
ear drum + ossicles + eustachian tube
inner ear
vibrations from the ossicles enter the cochlea\
contains the cochlea
pinna/auricle
outer ear; the visible part of the ear, collects sound waves
ear canal
outer ear; a passage comprised of bone and skin that leads to the eardrum
ear drum
middle ear; sound waves cause the ear drum to vibrate, the vibrations are transferred to the ossicles
ossicles
contains the three smallest bones in your body
- malleus, hammer
- incus, anvil
- stapes (stirrup), the smallest bone in the body
eustachian tube
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
cochlea
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
auditory nerve
inner ear; carries neural signals from the cochlea to the brain for interpretation
