P2

?
  • Created by: dkoning00
  • Created on: 08-06-16 18:31
How is some of the Sun's energy stored naturally on Earth?
In fossil fuels
1 of 115
How is harnessing wind energy indirect use of the Sun's energy?
Sun heats the air; hot air rises; air moves turbines
2 of 115
What are photocells?
Devices that generate electricity directly from the Sun's energy
3 of 115
What type of current is created by photocells?
DC (Direct Current)
4 of 115
What are photocells usually made of and why?
Silicon because it is a semi-conductor
5 of 115
Describe how photocells generate electricity
Silicon atom absorbs some of the energy form the Sun; some electrons are knocked of the atom's outer shell; the dislodged atoms flow around the circuit creating an electrical current
6 of 115
What three factors affect the power output of a photocell and how?
The surface area - the bigger the SA the more electricity produced. The light intensity - brighter light = more electricity. The distance from light source - the closer the source, the more intense the light is
7 of 115
Give three advantages and explanations of photocells
No moving parts so low maintenance and last longer. No need for power cables or fuels so good for low power devices e.g. calculators. Solar power cannot run out (it's renewable) and doesn't pollute the environment at all so is sustainable.
8 of 115
What is the biggest disadvantage o solar power?
When there's no sunlight (e.g. at night), there's no power so it is difficult to be totally reliant on it
9 of 115
Other than photocells, how can the Sun's energy be harnessed?
Curved mirrors can be focused to concentrate energy
10 of 115
In what ways can curved mirrors be used?
Food can be heated on the focal point in poor countries or ones without electricity. Large curved mirrors can be used to heat water pipes in order to generate steam that spins turbines and creates electricity
11 of 115
How can solar devices like solar panels and curved mirrors have increased efficiency?
If they track the Sun's movement across the sky and are pointed directly at the Sun then they capture the maximum amount of light and heat
12 of 115
What is passive solar heating?
The sun's energy being used to heat something directly i.e. without mirrors, lenses or photocells
13 of 115
Why is glass important in passive solar heating for a house?
Glass lets heat and light from the Sun into the house; it is absorbed by objects thus heating them up. Objects then remit the infrared energy but with a longer wavelength so they cannot escape, waves stay in the house to heat it - greenhouse effect
14 of 115
How can passive solar heating be used to heat water?
Matt black pipes in a glass box on the roof of a house are heated by the greenhouse effect which heats water being pumped through them - the water can then be used in radiators, washing machines etc.
15 of 115
How do wind farms produce electricity?
Sun heats air, air moves, kinetic energy turns turbine blades, spins generator and generates electrical current
16 of 115
What are the advantages of wind turbines?
They are cheap to run as they are reliable and wind is free. No polluting waste or products.Renewable energy source.
17 of 115
What are the disadvantages of wind farms?
1 coal power station=1500 wind turbines; visual & noise pollution - can spoil views and are noisy; wind isn't always fast enough to produce electricity; supply cannot be increased with demand; suitable sites are hard to find; expensive to build
18 of 115
What is the National Grid?
A network of pylons and power lines that transport electrical power across the country from power stations to homes and industry
19 of 115
Describe how power stations relase energy
Fuel is burned to turn water into steam in a boiler; steam moves through a turbine to trun the blades; the rotation is converted into electrical energy in a generator then transferred by cables
20 of 115
What are the advantages and disadvantages of fossil fuels being burned in power stations
They are readily available and are a concentrated source of energy. However, they release CO2 and cause acid rain plus we have no control over supply or price because they are bought from other countries
21 of 115
Advantages and disadvantages of Biomass fuels?
It is carbon neutral and can be quickly obtained, but it doesn't have as high of an energy value as fossil fuels
22 of 115
What is electromagnetic induction?
The creation of volatage (and possibly current) in a wire that is experiencing a change in the magnetic field
23 of 115
What is the dynamo effect and how is it used?
Using electromagnetic induction to turn kinetic energy into electrical energy - used in power stations by turbines creating electricity
24 of 115
What type of current is produced and why?
AC -because the movement causes alternating voltage
25 of 115
How can you get a bigger current and voltage?
Increase the strength of the magnet, the number of turns on the coil and the speed of the movement
26 of 115
How do generators work?
By turning a coil in a magnet to produce an AC current
27 of 115
In terms of voltage display, describe what happens to the waves when increasing the speed of rotation and why
They increase in both frequency and amplitude because the coil is passing the magnet more times per second and faster so there is a higher voltage
28 of 115
What is frequency measured in?
Hertz
29 of 115
Describe the difference between AC and DC current and give an example for each of a device that produces it
AC is constantly cycling from positive to negative voltages - created by generators. DC remains at one constant positive voltage - created by a battery or photocell
30 of 115
Give the equation for power loss
Power loss = Voltage x Current squared
31 of 115
Why is electricity transported at a high voltage across power lines from power stations?
Because power loss = voltage x current squared so a higher voltage means lower current and much less power loss - it is more efficient
32 of 115
How is voltage increased when leaving a power station?
By a Step-up transformer
33 of 115
Why must the voltage be decreased again before use and how is this done?
So it is safe and doesn't damage devices - step-down transformer
34 of 115
Why do transformers only work on AC current?
Because they use electromagnetic induction
35 of 115
Why do most power stations have low efficiency?
Because a lot of energy is wasted as heat and noise to the surroundings
36 of 115
What is power measured in?
Watts
37 of 115
Give the equation for power
Power (W) = Voltage (V) x Current (A)
38 of 115
What is a Kilowatt hour?
A unit of electrical energy used - the amount of electrical energy converted by a 1kW appliance left on for one hour
39 of 115
Give the equation for energy supplied in kW/H
Energy supplied = Power (kW) x Time (Hrs)
40 of 115
Cost of electricity =
Number of units used x Price per unit
41 of 115
What is 'off-peak' electricity and why do some people use it?
Using electrical appliances at night and in the early morning when few other people are using it. Electricity is cheaper off-peak so can reduce energy bills
42 of 115
What are some of the disadvantages?
Some argue that appliances could cause fires in a house if unattended over-night. Also it is inconvenient to only use certain appliances at night
43 of 115
Briefly describe the greenhouse effect
Short wavelength EM waves pass through the atmosphere from the sun; they heat the surface of the Earth which then re-emits longer wavelength EM waves; These are blocked from leaving atmosphere by greenhouse gases; the gases trap heat to raise temp.
44 of 115
Give the three main greenhouse gases
Carbon dioxide, Methane and Water vapour
45 of 115
Why are greenhouse gases both vital to our existence and a threat to it?
Without them the Earth would be too cold for life, however, too much will raise the average temp. which would also make the Earth uninhabitable
46 of 115
Why have Carbon dioxide levels risen in the last 200 years?
People use more energy (e.g. travel more in cars) which means more fossil fuels are burned; more trees are being cut down to make space so less photosynthesis; more people also means more respiration
47 of 115
Why have methane levels risen?
Cattle farming has increased which releases methane; increasing decaying waste in landfill; also released by volcanoes, wetland and animals
48 of 115
Why have water vapour levels rise?
Increased global temp. means more evaporation from water sources; power stations also produce water vapour
49 of 115
What are the three kinds of nuclear radiation?
Alpha, beta and gamma
50 of 115
What is ionisation?
Atoms losing or gaining electrons
51 of 115
How can radiation be dangerous to humans?
Molecules in cells ionise which damages DNA causing mutations and possibly cancer. Very high doses can also kill cells completely
52 of 115
What is the ionising power of each kind of radiation linked to and how?
How far it can penetrate - the more penetration before hitting the atom the less ionising it is
53 of 115
Describe the features and properties of Alpha decay
Big, heavy, positive isotopes consisting of 2 protons and 2 neutrons that moves slowly and as a result cannot penetrate far. Can be blocked by thin paper or skin but are heavily ionising.
54 of 115
Describe the features and properties of Beta decay
Small, fast moving, negative electron that penetrate further than alpha so less ionising. Can be stopped by a few mm of aluminium
55 of 115
Describe the features and properties of Gamma decay
Left over energy released from the nucleus as EM wave - no mass, no charge and can penetrate a long way so not very ionising at all. Can be stopped by thick concrete and a few cm of lead
56 of 115
Which type is most dangerous if ingested and why?
Alpha because it is the most heavily ionising so ca cause mutation and death of cells
57 of 115
How could you tell which kind of radiation is being emitted?
By measuring what materials and what thicknesses it can penetrate which a Geiger counter - e.g. if still measuring radioactivity beyond an aluminium plate then it must be gamma
58 of 115
How is Alpha radiation used in smoke detectors?
Small source of alpha radiation put close to 2 electrodes. Air between them is ionised allowing current to flow between electrodes completing a circuit. If smoke in air it absorbs the radiation so air isn't ionised, the circuit breaks & alarm sounds
59 of 115
Give three other uses of radiation and the types used
Medical and industrial tracers (gamma & beta), testing paper thickness (beta), treating cancer (gamma), sterilising medical equipment (gamma)
60 of 115
What is nuclear fission?
Splitting heavy nuclei to release energy
61 of 115
How is it used in a nuclear power station?
Unstable uranium atoms are split into two which releases energy as heat to heat water into steam which spins turbines attached to a generator
62 of 115
Give advantages of nuclear power
Lots of energy without CO2; much higher energy value with radioactive fuels - less fuel needed to make same amount of energy as fossil fuels; uranium is relatively cheap; High amounts of Uranium left to be extracted
63 of 115
Give disadvantages of nuclear power
Power stations are expensive to build & maintain; long start-up time; processing uranium causes pollution; always a risk of leaks and disaster; radioactive waste; decommissioning is expensive and difficult; uranium isn't renewable
64 of 115
What happens to used uranium fuel?
It can be reprocessed to get a smaller amount of uranium that can be re-used and a bit of plutonium that is used in nuclear weapons
65 of 115
What measures should be taken when handling radioactive material?
Avoid ingestion and inhalation; store safely in lead container; minimise exposure time; do not point it at yourself or others; do not touch with bare skin; keep at arm's length
66 of 115
What measures must industrial nuclear workers take?
Wearing full protective clothing with breathing apparatus; lead lined suits, walls and screens; using robotic equipment to remove human contact
67 of 115
How can radioactive waste be disposed of?
Low-level waste is buried in landfill, high level radioactive waste is treated, sealed in glass blocks, placed in metal canisters and buried deep underground
68 of 115
What are some of the difficulties with finding suitable locations to dispose of high-level radioactive waste?
The ground must be geologically stable (not prone to earthquakes etc.) and cannot be near a major water source
69 of 115
Why is most high-level waste kept on site at power plants?
Because finding a location is difficult and many people object to disposal so keeping it on site is easier
70 of 115
Why do nuclear power stations need to be kept secure?
Because they could be targets fro terrorist attacks and the material inside could be used to make 'dirty bombs'
71 of 115
List the contents of our solar system
The Sun, Mercury, Venus, Earth, Mars, (Asteroid Belt), Jupiter, Saturn, Uranus, Neptune, (Pluto)
72 of 115
What keeps planets in orbit around a star?
A combination of the planet's forwards motion perpendicular to the star and the gravity pulling the planet directly towards the star resulting in circular motion
73 of 115
What is this force known as?
Centripetal force
74 of 115
What is the asteroid belt and why did it form?
Millions or rocks in a ring around the Sun between Mars and Jupiter - these rocks should have come together to form a planet in the early stages of the solar system but Jupiter's gravity kept interfering so they didn't come together
75 of 115
What are meteors?
Rocks or dust that enter the Earth's atmosphere then burn up appearing as 'shooting stars'
76 of 115
What are meteorites?
Pieces of a meteor that did not completely burn up when entering the atmosphere impacting the surface of the Earth.
77 of 115
How can meteorites be dangerous?
On impact they can create craters, start fires and throw large amounts of dust and smoke into the atmosphere causing climate change
78 of 115
Give an example of a historical meteorite impact and its effects
Around 65 million years ago an asteroid roughly 10km in diameter impacted the Yucatan peninsular in Mexico which kicked dust and smoke up into the atmosphere causing global temperatures to drop drastically. This resulted in extinction of many species
79 of 115
What evidence can be used to show where asteroids have previously landed?
Craters in the ground; layers of unusual rock/elements that were 'imported' by an asteroid; sudden changes in fossil numbers as species were extinct
80 of 115
What are comets?
Balls of dust, ice and rock which orbit stars in very elongated ellipses often in different planes from the planets
81 of 115
Briefly describe the stages of a comet's orbit starting from the Sun
Comet travels very quickly around the Sun close to it; sling-shot away at high speed; The further away it gets, the slower it becomes dues to gravity; it turns back towards the Sun due to its attraction accelerating; highest speed when it reaches Sun
82 of 115
Why does a comet's acceleration increase as it gets closer to the Sun?
Because the gravitational attraction is stronger as it gets closer
83 of 115
What are Near Earth Objects?
Asteroids or comets which could be on a collision course with Earth or pass close by it
84 of 115
How can they be dangerous?
If a large NEO impacted Earth it could cause explosions, tsunamis, earthquakes, a nuclear winter and the end of every human ever... like seriously
85 of 115
How are NEOs monitored and how could an impact be averted?
Monitored using telescopes and satellites - if a powerful enough explosion occur close enough to a large asteroid it could knock it off course e.g. launching a nuclear missile... Failing that, Bruce Willis
86 of 115
Describe briefly how scientists believe our moon was formed
A Mars-sized planet (Thea) collided with the Earth; the iron cores merged under intense heat and pressure to form modern Earth; less dense surface material ejected into space; rocks orbited Earth and forged together to make the moon in orbit
87 of 115
What evidence is there to support this theory?
The Moon has a lower density than Earth and has no iron core suggesting it is made of crust rock and Moon rock contains few materials that evaporate easily meaning it was formed under intense heat
88 of 115
What galaxy is our solar system in?
The Milky Way
89 of 115
What is a light year?
The distance light travels through a vacuum in one year
90 of 115
Why do scientists use light years instead of kilometers when measuring space?
Because things are so far apart that they would have to use ridiculously large measures of kilometers. Light years are so much larger that they a more appropriate unit of measurement
91 of 115
Roughly how far is one light year?
Over 9 quadrillion
92 of 115
What is a black hole?
When very massive stars run out of fuel they can explode leaving an incredibly dense core - nothing can escape its gravitational attraction (not even light)
93 of 115
What difficulties are associated with manned space travel?
The craft must carry lots of food, water and oxygen; temperature and gas content must also be regulated; craft must have radioactive shielding; long periods of zero gravity diminish muscle ad bone strength; psychological stress
94 of 115
What are the three types of probe mission and what are they used for?
Fly-by - gathers data on temp. magnetic & gravity attraction and radiation without entering atmosphere. Entering atmosphere - collects similar data as well as atmospherical content. Landing - rovers land on surface to collect physical samples
95 of 115
Give advantages of unmanned spacecraft
Don't have to carry food, water or oxygen; can withstand conditions lethal to humans; no people taking up space and weight; cheaper, less safety equipment etc.; no potential for loss of life
96 of 115
Give disadvantages of unmanned spacecraft
Probes cannot think for themselves whereas humans can solve problems to survive; cannot do maintenance/repairs like astronauts e.g. Apollo 13, Discovery etc.
97 of 115
What two ways can data be sent back to Earth and when are they appropriate?
'Beaming' - sending digital data over long distances by radio waves from far away probes usually; Physical data can be sent back if the craft returns - astronauts collect moon rock etc.
98 of 115
Why is it believed that the universe is expanding?
Galaxies all appear to be moving away from each other
99 of 115
What is red shift?
Light from distant galaxies have lower frequencies than expected (shifted towards red end of spectrum). This means that the sources of the light (galaxies) are moving away from us very quickly
100 of 115
Why do more distant galaxies have greater red shift?
Because they are moving away faster than nearer galaxies concluding that the universe is expanding in all directions
101 of 115
What is Cosmic Microwave Background Radiation (CMBR)?
Scientists detect low frequency microwave radiation in space from all directions. It is strong evidence supporting the Big Bang Theory
102 of 115
Briefly describe the Big Bang Theory
Roughly 14 billion years ago all matter in the universe occupied an exceptionally small space (smaller than a pinhead); it then 'exploded' thus expanding the space and matter in all directions continuously
103 of 115
What is a nebular?
A huge cloud of dust and gas in space
104 of 115
How are Protostars formed?
Nebulars gain gravitational attraction and spiral together creating high pressure and heat
105 of 115
When is a main sequence star formed?
When the temperature gets high enough for hydrogen to undergo thermonuclear fusion to form helium nucle and release huge amounts of heat and light energy. The fusion provides outward pressure to counter gravity keeping the star stable
106 of 115
What happens when the hydrogen runs out?
Fusion stops so the star swells and the surface cools - a red giant is formed
107 of 115
Describe the rest of the life-cycle for a small to medium sized star
The red giant ejects it outer layers of dust and gas to become a planetary nebular; hot, dense core is left behind (white dwarf) until it cools and fades into a black dwarf and disappears
108 of 115
Describe the rest of the life-cycle for a more massive star
Forms super red giant which glows brightly and contracts and expands several times as heavier elements are made by fusion; explodes into a supernova; very dense core is left behind as a neutron star; if big enough, it will collapse into a black hole
109 of 115
What does geocentric mean and what was the Ptolemaic model?
Earth centred - Model of the solar system used by the Greeks with the Sun, Moon, planets and stars all orbiting the Earth in the centre
110 of 115
What does Heliocentric mean and what is the Coppernican model?
Sun centred - Model of the solar system introduced by Coppernicus in 1543 with the sun in the middle being orbited by the planets in perfect circles
111 of 115
How did Galileo find good evidence to support Coppernicus?
By studying Jupiter with a telescope he noticed some stars didn't ever move away from Jupiter. He figured out these stars were actually moons orbiting Jupiter which proved that not everything orbited Earth. He also noticed phases of Venus
112 of 115
Why wasn't the Coppernican model initially accepted?
Because it contradicted an accepted theory that had been around for centuries, also it was condemed by the church
113 of 115
How did it come to be accepted?
With the development of new technologies more evidence could be gathered
114 of 115
How is the modern model slightly different to the Coppernican Model?
It still has the planets all orbiting the sun but it slightly elliptical orbits, also, the Coppernican model claimed the stars were fixed around the solar system but we now know this to not be true
115 of 115

Other cards in this set

Card 2

Front

How is harnessing wind energy indirect use of the Sun's energy?

Back

Sun heats the air; hot air rises; air moves turbines

Card 3

Front

What are photocells?

Back

Preview of the front of card 3

Card 4

Front

What type of current is created by photocells?

Back

Preview of the front of card 4

Card 5

Front

What are photocells usually made of and why?

Back

Preview of the front of card 5
View more cards

Comments

Bushra Patel

Report

This is pretty good set, thanks loads, I've been trying to find a good P2 set and this is excellent 'cause it's shorthand and easy to remember, so thanks loads 

Similar Physics resources:

See all Physics resources »See all P2 resources »