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Physics > P2- Living For The Future > Flashcards

P2- Living For The Future Flashcards

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0
Q

What is the one disadvantage of photocells?

A

They do not produce electricity when it is dark or too cloudy

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1
Q

What are the advantages of photocells?

A

They are robust and do not need much maintenance
They need no fuel and do not need long power cables
They cause no pollution and do not contribute to global warming
They use a renewable energy resource

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2
Q

How do photocells work and what are they?

A

A photocell contains two pieces of silicone joined together to make a p-n junction.
One piece has an impurity add to produce an excess of free electrons n-type silicon.
The other piece has a different impurity added to produce an absence of free electrons p-type silicon
Sunlight contains energy packets called photons.
Photons cause free electrons to move producing an electric current

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3
Q

What does the output of a photocell depend on?

A

Light intensity
Surface area exposed
Distance from light source

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4
Q

What is passive solar heating and how does it work?

A

The sun is very hot and produces infrared radiation with a very short wavelength.
Glass is transparent to this short wavelength radiation.
The walls and floor inside a building absorb this radiation, warm up and re radiate infrared radiation
The walls and floor are not as hot as the sun and the wavelength radiated is therefore longer.
Glass reflects this longer wavelength radiation back inside the building.

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5
Q

In passive solar heating, which wave do the windows need to face?

A

In Southern Hemisphere, large windows in a house need to face. Roth towards the sun.
In northern hemisphere they face south.

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6
Q

How can solar reflectors always face the sun?

A

They are moved by computer.

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7
Q

Advantages and disadvantages of wind turbines and wind farms

A

Renewable form of energy
But depends on speed of wind
Wind turbines don’t work if there is no wind or if the speed is too great.
Wind farms don’t contribute to global warming or pollute the atmosphere.
But can be noisy, take up a lot of space and people sometimes complain they spoil the view.

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8
Q

How can the current from A dynamo be increased?

A

Using a stronger magnet
Increasing the number of turns on the coil
Rotating the magnet faster

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9
Q

What can the output from a dynamo be displayed on?

A

Oscilloscope.

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10
Q

What does an oscilloscope show?

A

An oscilloscope trace shows how the current produced by the dynamo varies with time.

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11
Q

What is the time of one complete cycle of a dynamo/oscilloscope called?

A

Alternating current.

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12
Q

What is a simple generator?

A

Consists of a coil of wire rotating between the poles of a magnet.
The coil cuts through the magnetic field as it spins
A current is produced in the coil
A current can be produces if the coil remains stationary and the magnets move.
Generators at power stations work on the same principle.

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13
Q

I’m conventional power stations, how do they run?

A

Fuel is used to heat water
Water boils to produce steam
Steam at high pressure turns turbine
The turbine drives a generator

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14
Q

What is efficiency?

A

A measure of how well a device transfers energy

Energy in a power station is lost in the boilers, generators and cooling towers.

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15
Q

Most wavelengths of electromagnetic radiation can pass through the earths atmosphere but what?

A

Infrared radiation is absorbed

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16
Q

Carbon dioxide occurs naturally in the atmosphere as a result of…

A 
Natural forest fires
Volcanic eruptions
Decay of dead plants and animal matter
It's escape from the oceans
Respiration
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17
Q

Man made carbon dioxide is caused by….

A

Burning fossil fuels
Waste incineration
Deforestation
Cement manufacture

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18
Q

Water vapour is the most significant greenhouse gas because…

A

Almost all of water vapour occurs naturally
A mere 0.001 percent comes from human activity
Half of the greenhouse effect is due to water vapour and a further quarter is due to clouds.

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19
Q

Methane is produced when organic matter decomposes in an environment lacking oxygen. Eg….

A

Natural sources include wetlands, termites and oceans.
Man made sources include the mining and burning if fossil fuels, the digestive process in animals such as cattle, rice paddies and the burying of waste in landfills.

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20
Q

The electromagnetic radiation from the sun has what wavelength?

A

Short.

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21
Q

The suns radiation is absorbed by and warms the earth. Then what happens?

A

The earth then re radiates the energy as infrared radiation with a longer wavelength. This longer wavelength radiation is absorbed by the greenhouse gases which warms our atmosphere.

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22
Q

Dust in the atmosphere can have opposite effects, eg…

A

The smoke from the factories reflects radiation from the town back to earth. The temperature rises as a result.
The ash cloud from a volcanoe reflects radiation from the sun back into space. The temperature falls as a result.

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23
Q

It is important to make depictions on global warming based on what?

A

Scientific evidence not the basis of unsubstantiated opinions.

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24
Q

What evidence is there to show climate change is happening?

A

The temperature of the earth has increased steadily during the
Past 200 years

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25
Q

What don’t scientists agree on about global warming?

A

The extent to which human activity has contributed.

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26
Q

Why do we pay less for electricity during the night?

A

Because it still has to be produced but not a lot of people use it.

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27
Q

What is the unit for electrical energy around the home?

A

kWh

Kilowatt-hour

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28
Q

The choice of energy source depends on what?

A

Availability
Ease of extraction
Effect on the environment
Associated risks

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29
Q

What is the national grid?

A

A series of transformers and power lines that transport electricity from the power station to the consumer.

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30
Q

What are step up transformers?

A

Used to increase the voltage.

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31
Q

What can a high voltage lead to?

A

Reduced energy loss
Reduced distribution costs
Cheaper electricity for consumers

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32
Q

What do step down transformers do?

A

Step down the voltage to a more suitable level for the consumer.

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33
Q

When a current passes through a wire what happens?

A

The wire gets hot

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34
Q

The greater the current, the hotter the…

A

Wire

35
Q

When a transformer increases the voltage, the current is reduced which means…

A

There is less heating effect and therefore less energy lost to the environment.

36
Q

When are atoms neutral?

A

When they have the same protons and electrons

37
Q

The formation of ions can cause chemical reactions. Such reactions can…

A

Disrupt the normal behaviour of molecules inside the body. Eg they may cause strands of DNA to break or change, protein molecules may change their shape and these effects are potentially harmful

38
Q

What are he three radiations and where do they come from?

A

Alpha beta and gamma, nucleus of an atom.

39
Q

Which radiation causes the most ionisation? Which causes the least?

A

Most alpha

Least gamma

40
Q

What are the radiations absorbed by?

A

Alpha few cm of air, paper, skin

41
Q

What is beta absorbed by?

A

1m of air, mm’s of aluminium

42
Q

What is gamma absorbed by?

A

Cm’s of lead.

43
Q

Experiments can be done to identify each type of radiation from it’s penetrating power, but what needs to be taken into account?

A

Background radiation.

44
Q

How do smoke alarms work?

A

They contain a source of alpha.
The radiation ionises the oxygen and nitrogen atoms in the air which causes a very small electric current that is detected. When smoke fills the detector in the alarm during a fire, the air is not so ionised, the current is less and the alarm sounds.

45
Q

What can beta be used for? How?

A

Thickness In A paper rolling mill can be controlled using a source of beta radiation and a detector.
The amount of radiation passing through the sheet is monitored and the pressure on the rollers adjusts accordingly.

46
Q

What are the uses of gamma radiation?

A

Kills microbes and bacteria so it can be used for sterilising medical instruments. It can be used to check for leaks in pipes and blockages.

47
Q

The passage of blood and other substances around the body using…

A

A beta or gamma source.

48
Q

What is the waste product from nuclear reactors which can be used to make nuclear bombs?

A

Plutonium.

49
Q

How can radioactive waste be disposed?

A

Low level radioactive waste can be buried in landfill sites.
High level waste is encased in glass and buried deep underground or reprocessed.
Radioactive waste can remain radioactive for thousands of years. It must be stored where it cannot leak into natural underground water supplied and hence into lakes and rivers. It is not suitable for making nuclear bombs, but it could be used by terrorists to contaminate water supplies or areas of land.

50
Q

What are the advantages and disadvantages of nuclear power stations?

A

Adv
Fossil fuel reserves are not used and no greenhouse gasses are discharged into the atmosphere.
Disadv
It’s very high maintenance and decommissioning costs, the risk of accidents is similar to that of Chernobyl.

51
Q

How do comets orbit?

A

Elliptical

They pass inside the orbit of mercury and go out well beyond the orbit of Pluto.

52
Q

What is a meteor made of?

A

Grains of dust they burn ds they pass throughout earths atmosphere. They heat the air around them which glows and the streak is known as a shooting star.

53
Q

What are black holes?

A

They are formed where large stars used to be
You cannot see a black hole because light cannot escape from it
It has a very large mass but a very small size

54
Q

How do moons orbit?

A

Moons orbit planets and planets orbit stars because centripetal force acts on them
Centripetal force acts towards the centre of the circular orbit
Gravitational attraction is the source of the centripetal force.

55
Q

Unmanned probes can go….

A

Where conditions are deadly for humans

56
Q

Spacecrafts carrying humans have to have ….

A

Large amounts of food, water and oxygen aboard.

57
Q

Astronauts can wear normal clothing in a ….

A

Pressurised spacecraft

58
Q

Outside the spacecraft what do astronauts have to wear?

A

Special spacesuits
A dark visor stops an astronaut being blinded
The suit is pressurised and has an oxygen supply for breathing
The surface of the suit facing towards the sun can reach 120 degrees
The surface of the suit facing away from the sun can’t each -160 degrees

59
Q

When travelling in space, astronauts are subjected to…

A

Lower gravitational forces than on earth

60
Q

Unmanned spacecrafts cost less and do not put astronauts lives at risk but…

A

They have to be very reliable because there is usually no way of repairing them when they break down.

61
Q

Distances I. Space are very…

A

Large

62
Q

Light travels at…

A

300,000km/s

63
Q

Light from the sun takes how long to reach earth?

A

8 minutes

64
Q

Light from the next nearest star (Proxima Centauri) takes …

A

4.22 years to reach earth.

65
Q

What is a light year?

A

The distance light travels in one year

66
Q

America plans a mission to Mars after 2020 at a cost of…

A

£400 billion

67
Q

What are asteroids?

A

Mini planets or planetoids orbiting the sun.
Most orbit between mars and Jupiter
They are large rocks that were left over from the foundation of the solar system

68
Q

All bodies in space, including plants were formed when…

A

Clouds of gas and dust collapsed together due to gravitational forces of attraction.

69
Q

The mass of an object determines it’s..

A

Gravitational force

70
Q

Asteroids have relatively low…

A

Masses compared to the mass of Jupiter

71
Q

Jupiters gravitational force prevents…

A

Asteroids from joining together to form another planet.

72
Q

Scientists believe our moon was a result of..

A

The collision between two planets in the same orbit. The iron core of the other planet melted and joined with earths core, less dense rocks began to orbit and they joined together to form our moon.

73
Q

What is the scientific evidence to support that our moon was two planets?

A

The average density of earth is 5500kg/m^3 while that if the moon is only 330 kg/m^3
There is no iron in the moon
The moon has exactly the same oxygen composition as earth, but rocks on mars and meteorites from other parts of the solar system have different oxygen compositions

74
Q

Geologist examine evidence to support the theory that asteroids have collided with earth. What is this evidence?(3)

A
  • Near to a crater thought to have resulted from an asteroid impact, they found quantities of the metal iridium. A metal not normally found in the earths crust but common in meteorites.
  • many fossils are found below the layer of iridium, but few fossils are found above it
  • tsunamis have disturbed the fossil layers, carrying some fossil fragments up to 300 km inland
75
Q

Most comets pass inside the orbit of mercury and well beyond the orbit of Pluto. Explain it’s orbit…

A

As the comet passes close to the sun, the ice melts and the solar winds blow the dust into the comments tail which always points away front the sun.
The speed of a comet increases as it approaches the Sun and decreases as it gets further away. This is because of the changing gravitational attraction.

76
Q

What is a neo?

A

Near earth object

77
Q

If a neo is in a collision course with earth, what would happen? How can we prevent is?

A

It would be the end of all life on earth.
To avoid this, one option would be to explode a rocket near to the neo which could alter its course enough to miss earth.

78
Q

Almost all of the galaxies are moving how?

A

Moving away from each other with the further out galaxies moving the fastest

79
Q

With the help of the newly invented telescope, what did Galileo discover?

A

Four moons orbiting Jupiter. This confirmed that not everything orbited the earth and supported Copernicus’ idea that planets orbit the sun.

80
Q

What did the Roman Catholic Church think of galileo’s model?

A

They believed the earth was at the centre of the universe and it was a very long time before his idea was accepted.

81
Q

In the 17th century, what was Newton doing?

A

Working on his theory of universal gravitation which suggested that all bodies attract one another.

82
Q

Today, we believe that gravitational collapse is prevented because….

A

The universe in constantly expanding as a result of the Big Bang.

83
Q

What is red shift?

A

When a source of light is moving away from its observer, it’s wavelength appears to increase which shifts light towards the red end of the spectrum. (Red shift)
When scientists look at the sun, there is a patter. Of lines across the spectrum. The same pattern Is observed when they look at light from distant stars but it is closer to the red end of the spectrum.
Scientists can use information from red shift to work out the age of the universe.

84
Q

Explain the life of a star

A

The swirling cloud of dust and gas is a nebula.
Nebula clouds are pulled together by gravity and. As the spinning ball of gas starts to get hot, it glows. This protostar cannot be seen because of the dust cloud.
Gravity causes the star to become smaller, hotter and brighter and after millions of years ,the core temperature is hot enough for nuclear fusion to take place. As hydrogen nuclei join together to form helium nuclei, energy is released and the star continues to shine while there is enough hydrogen. Small stars shine for longer than large stars because they have less hydrogen but use it up at a slower rate.
MEDIUM
Medium sized stars like the sun, become a red giant. While the core contracts, the outer part cooks and changes colour from yellow to red and expands. Gas shells, called planetary nebula are thrown out. The core be ones a white dwarf shining very brightly but eventually cools to become a black dwarf.
LARGE
Become red supergiants. As the core contracts and the outer part expands and suddenly the core collapses to form a neutron star and there is an explosion called a supernova. Neutron stars are very dense. Remnants from a supernova can merge to form a new star. The core of the neutron star continues to collapse, becomes even more dense and could form a black hole.

85
Q

How do we know black holes have a large density and a very strong gravitational pull?

A

It has a very large mass concentrated in a small volume so it has a large density and it’s large mass means it has a very strong gravitational pull.

Physics (5 decks)

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