P8 - global challenges Flashcards
what is a circuit breaker?
an electrical switch designed to protect an electrical circuit from damage
what is an earth wire?
a safety wire that stops the appliance becoming live
what is a fuse?
thin wire that melts if current too high
what is an iron core?
the main structure of the transformer that links the alternative magnetic field from the primary coil to the secondary coil
what is a live wire?
carries high voltage (230V)
what is the national grid?
the power stations, wires, pylons an transformers that supply electricity to everyone in the UK
what is a neutral wire?
completes the circuit
what does non-renewable mean?
energy sources that will run out
what is a primary coil?
the wire carrying the current to the transformer
what does renewable mean?
energy sources that will not run out (in the next million years or so)
what is resistance?
a measure of how easy it is for current to flow
what is a secondary coil?
the wire carrying the current away from the transformer
what is a step-down transformer?
decreases the p.d. from primary coil to secondary coil back to safer levels; located near to homes
what is a step-up transformer?
increases p.d. from primary to secondary coils; located next to power station; used to reduce heating losses in the national grid
what are the main energy resources?
- fossil fuels (coal, oil and gas)
- nuclear fission
- solar
- hydroelectricity
- wind
- tidal
- biofuels
are fossil fuels renewable or non-renewable?
non-renewable
is nuclear fission renewable or non-renewable?
non-renewable
is solar renewable or non-renewable?
renewable
is hydroelectricity renewable or non-renewable?
renewable
is wind renewable or non-renewable?
renewable
is tidal renewable or non-renewable?
renewable
are biofuels renewable or non-renewable?
renewable
what type of energy store do fossil fuels have?
chemical
what type of energy store does nuclear fission have?
nuclear
what type of energy store does solar have?
nuclear
what type of energy store does hydroelectricity have?
gravitational
what type of energy store does wind have?
kinetic
what type of energy store does tidal have?
kinetic
what type of energy store do biofuels have?
chemical
what are the advantages and disadvantages of fossil fuels?
advantages:
- cheap
- reliable 24 hours a day
disadvantages:
- CO2 produced
- coal causes acid rain
what are the advantages and disadvantages of nuclear fission?
advantages:
- no CO2 produced
- reliable 24 hours a day
disadvantages:
- very expensive
- radioactive waste remains dangerous for 1000s of years
what are the advantages and disadvantages of solar?
advantages:
- no CO2 produced
- used in remote areas
disadvantages:
- no electricity at night
- takes up a lot of land
what are the advantages and disadvantages of hydroelectricity?
advantages:
- no CO2 produced
- reliable 24 hours a day
disadvantages:
- land has to be flooded behind dam (ecological destruction)
what are the advantages and disadvantages of wind?
advantages:
- no CO2 produced
disadvantages:
- no electricity in calm weather
- take up a lot of land/sea
- eyesore
what are the advantages and disadvantages of tidal?
advantages:
- no CO2 produced
- reliable 24 hours a day
disadvantages:
- disruption to ecosystems by blocking river estuaries
- expensive
what are the advantages and disadvantages of biofuels?
advantages:
- carbon neutral
- reliable 24 hours a day
disadvantages:
- crops which were used for food are now used for fuel; rise in food prices
- large amount of land required for crops
- CO2 emitted in transport and processing
how are fossil fuels used to generate electricity?
burnt to make steam, which turns a turbine, which turns a generator
how is nuclear fission used to generate electricity?
nuclear fission releases heat to make steam, which turns a turbine, which turns a generator
how is solar used to generate electricity?
light to electrical
- light from the sun causing electrons to become free in a silicon, resulting in a current
how is hydroelectricity to generate electricity?
water runs through a pipe to a turbine, which then turns a generator
how is wind used to generate electricity?
wind turns a turbine which turns a generator
how is tidal used to generate electricity?
a tidal river is blocked, the water then flows through a pipe to a turbine, which turns a generator
how are biofuels used to generate electricity?
- burnt to generate steam, which turns a turbine, which turns a generator
- alternatively used in cars when mixed with petrol
how does a power station generate electricity?
- fuel is burnt
- steam is produced
- kinetic energy from steam turns a turbine
- the turbine turns magnets in the generator
- this induces p.d. in the stationary coils of the generator of about 25kV
between 1820 and 1900 why would biofuels have been used the most?
people used wood for heating because it was readily available and free; there was no electricity
why did energy consumption increase dramatically after 1900?
- world population increased dramatically
- electricity generation was invented
- Industrial Revolution throughout the world
why were the most widely used fuels from 1900 onwards fossil fuels?
- they are easily available and cheap
- used in transport
why does nuclear power still remain only a small fraction, despite starting in the 1960s?
nuclear power was only harnessed in the 1960s and is expensive and potentially dangerous so many countries choose not to use it
what do governments need to consider when deciding on which energy sources to use in the future?
- cost
- environmental impact
- carbon dioxide emissions
- how long the resources will last
why is coal use decreasing?
produces the most CO2 from any fossil fuel so contributes mot to climate change
why has renewable use increased?
- technology now available
- renewables becoming cheaper, so governments switching to these to reduce greenhouse gas emissions
why do gas and nuclear remain roughly constant?
- neither are ideal
- gas produces the least CO2 compared to other fossil fuels
- both gas and nuclear provide a constant, reliable supply of electricity that currently renewables cannot
what does high current cause?
heating
how can you tell the difference between a step-up transformer and a step-down transformer?
step-up has more turns on the secondary coil than the primary
how do transformers work?
- an alternating p.d. causes and alternating input current in the primary coil
- this causes an alternating magnetic field
- this magnetises the iron core
- the secondary coil now experiences the alternating magnetic field
- this induces a p.d. in the secondary coil and therefore an alternating output current
why would a direct current not work in a transformer?
- direct current would create an unchanging magnetic field and so no p.d. would be induced
- this is the same as holding a magnet stationary inside a coil of wire
in what two ways is electricity dangerous?
- can cause a fire
- can electrocute you
what does the number on a fuse tell you?
the maximum current before they melt
what would happen if a fault occurs in a toaster without an earth wire?
- a wire inside the toaster breaks and touches th metal case
- we say the metal case is ‘live’
- if someone touches it, current will flow through them to earth and they will be electrocuted
what would happen if a fault occurs in a toaster with an earth wire?
- earth wire provides a very low resistance path to earth
- therefore a large current flows through the circuit (to earth), which melts the fuse and breaks the circuit
- it’s now safe
how should you choose the correct fuse?
fuse rating should be slightly above the operating current
how do circuit breakers work?
- the solenoid in a circuit breaker creates an electromagnet
- as current increases, electromagnet becomes very strong so pulls the armature across, therefore opening the switch and breaking the circuit
- it can be reset easily
what is the Big Bang theory?
the universe must have originated at a single point and then expanded (and has been expanding ever since)
what is a black hole?
a region of space having a gravitational field so intense that no matter or radiation can escape
what is a centripetal force?
the name given to a force directed towards the centre of a circle, allowing an object to move in a circular motion
what is climate change?
a large-scale, long-term shift in the planet’s weather patterns and average temperatures
what is cosmic microwave background radiation?
leftover radiation from the Big Bang
what is the doppler effect?
the change in the observed wavelength and frequency of waves due to the apparent motion of source of waves
what is a main sequence star?
a star that has a hot, dense core which fuses hydrogen into helium to produce energy
what is a neutron star?
the collapsed core of a red supergiant; it consists entirely of neutrons
what is a nebula?
a cloud of gas and dust in outer space
what is a protostar?
a collection of gas and dust in space with high temperature
what are p-waves?
earthquake wave that can travel through solid and liquid; fast; longitudinal
what is a satellite?
an object which orbits a planet
what is a supernova?
an exploding star
what are s-waves?
earthquake wave that only travels through liquid; slow; transverse
list the electromagnetic spectrum in order from longest to shortest wavelength
- radio waves
- microwaves
- infrared
- visible light
- ultraviolet
- x-rays
- gamma rays
list the colour spectrum in order from longest to shortest wavelength
- red
- orange
- yellow
- green
- blue
- indigo
- violet
what does the type of radiation an object emits depend on?
its temperature; the hotter the temperature, the shorter the wavelength
what are the greenhouse gases?
- water vapour
- carbon dioxide
- methane
how does the natural greenhouse effect work?
- the earth absorbs short wavelength infrared radiation from the sun
- the warm earth emits longer wavelength infrared back to space
- greenhouse gases absorb the long wavelength infrared and heat up
how does the human enhanced greenhouse effect work?
- increased greenhouse gases in atmosphere = more radiation absorbed, instead of being emitted straight back to space; some of this infrared is re-emitted back to earth
- when this happens, earth will increase in temperature
- this is global warming, causing the climate to change
what four things can waves do when they reach a boundary between layers?
- reflected
- refracted
- absorbed
- transmitted
what does reflected mean?
angle of incidence = angle of reflection
what does refracted mean?
waves change direction at a boundary between materials as they change speed due to change in density of material
what does absorbed mean?
the wave energy is absorbed by material causing it to heat up
what does transmitted mean?
material lets wave through with no change to material or wave
how do we know so much about the structure of the ocean floor?
sonar (sound, navigation and ranging)
how does sonar work?
- the time for the sound echo to return is recorded
- distance is then calculated using s = d/t
- d = st then divide by 2 as sound has travelled there and back
what are the layers within the earth called?
- inner core
- outer core
- mantle
- crust
if an earthquake occurs on the other side of the world, we will only detect p-waves in salisbury; what does this tell us about the core of the earth?
the outer core must be made of liquid
explain what we know due to s-wave and p-wave patterns?
- scientists use info about time for waves to arrive in various locations to determine where earthquake occurred/types of material waves travelled through
- always large s-wave shadow, tells us outer core = liquid
- p-wave shadow due to p-waves refracting in liquid outer core due to density change
- density increases with depth as pressure increases with depth
list the plants in our solar system (closest to furthest)
- mercury
- venus
- earth
- mars
- jupiter
- saturn
- uranus
- neptune
what are asteroids?
rocky objects that can massively range in size
where are asteroids located?
between Jupiter an mars
what are natural satellites also known as?
moons
what do geostationary satellites do?
- stay above same location above equator
- take 24 hours to complete orbit
what do polar satellites do?
- orbit above the poles
- take about 2 hours to orbit earth
- orbit many times a day so can ‘view’ whole earth as rotates beneath them
what are some examples of uses of geostationary satellites?
- satellite television
- communications
what are some examples of uses of polar satellites?
- military (spying)
- observation of earth
- weather monitoring
are geostationary or polar satellites closer to the earth?
polar
what is circular motion?
in circular motion, direction therefore velocity is changing; changing velocity = acceleration
what does newton’s 2nd law tell us?
an object will remain at constant velocity unless acted on by a resultant force
what is the resultant force known as in circular motion?
the centripetal force, acting towards centre of circle (not a force in its own right but provided by another force)
what are some conclusions from the bung on string experiment?
- for stable orbit, faster object must be in orbit with small radius
- however, if planet were to further speed up, would shoot off into outer space ass gravitational force not strong enough to keep in orbit
- if slowed down, would circle in towards sun
describe the formation of planets
- in protostar phase, most matter collects at centre to form star
- leftover matter rotates around new star in disk
- matter in disk eventually clumps together
- heavier matter collects nearer new star to form rocky planets
- lighter matter collects on outer part of disk to from gas planets
what is the life cycle of a smaller star?
- nebula
- protostar
- main sequence
- red giant
- white dwarf
- black dwarf
what is the life cycle of a bigger star?
- nebula
- protostar
- main sequence
- red supergiants
- supernova
- neutron star
- black hole
what happens at the nebula stage?
- very large clouds of dust/gas (often 99% hydrogen)
- gravitation attraction between particles forms clumps of matter
- as clumps grow, have stronger gravitational pull on other matter
what happens at the protostar stage?
- as cloud collapses, centre becomes very hot/dense, emitting light
- gravitational potential energy converted into thermal
- eventually becomes hot enough for fusion of hydrogen nuclei to take place - a star is born
what happens at the main sequence stage?
- radiation produced at centre of star provides outwards force that counteracts gravitational collapse of new star
- two forces are balanced, star is in equilibrium
- spends most of ‘life’ in this phase
- eventually star will run out of hydrogen to fuse in the core
- then fusion stops and gravitational force will take over
after the main sequence stage, what happens in stars like the sun or smaller?
- core becomes dense and outer layers of star expand/ cool
- since outer layers cooler, star looks redder and bigger
- now a red giant
- eventually outer layers will drift away and leave behind the hot core
- now a white dwarf
- outer layers form planetary nebula around white dwarf
- eventually core cools and stops emitting light
- now a black dwarf
after the main sequence stage, what happens in stars larger than the sun?
- big enough to star fusing helium
- reconfigure structure, outer layers swell/cool while internal layers fuse helium
- become red supergiant
- eventually red supergiant can no longer fuse elements (can fuse up to iron)
- when fusion stops, nothing to counteract gravitational collapse so outer layers collapse inwards
- when material collides with core, rebounds with explosive energy, can produce enough light to outshine entire galaxy
- now a supernova
how do stars become neutron stars?
- during supernova, core of red supergiant compressed so much that protons in core turn into neutrons so can be squashed closer together
how can black holes form?
- if core compressed enough, density increases so much that gravitational pull of core is great enough not even light can escape
- if light can’t escape then left over core cannot be seen, hence why its called a black hole
what are the two main competing theories of the universe?
- steady state theory
- big bang theory
what is the steady state theory?
the universe has always existed and matter is continually being created
what is the Big Bang theory?
suggests all of the current and past matter in the universe came into existence at the same time, roughly 13.8 billion years ago
what happens in the doppler effect in sound?
- as a car approaches us the sound waves are squashed together, we hear more waves per second so the frequency is greater (higher pitch)
- as a car moves away the sound waves are stretched out, we hear less waves per second so the frequency is lower (lower pitch)
what happens in the doppler effect in light?
- when a source moves away from an observer, the observer sees the wavelength lengthen (red shift)
- when a source moves towards an observer, the observer sees the wavelength shorten (blue shift)
what is the absorption spectra?
- if the light source is moving away, the absorption spectra looks a little different
- we observe a longer wavelength and say it is ‘red-shifted’
when Edwin Hubble noticed that the spectra from more distant galaxies had a greater redshift, what did it suggest?
- all galaxies are moving away from us and each other
- the furthest galaxies are moving away the fastest
what conclusion can be drawn from Edwin Hubble’s observings?
the universe is expanding
what must the universe have originated from if it’s expanding?
a single point
what is an argument against the Big Bang theory?
there should be further evidence of an explosion of this scale still detectable in the universe
