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91 Cards in this Set

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Adv of photocells (4)

- are robust, don't need maintained


- don't need fuel and no long power cables


- no pollution caused = doesn't increase global warming


- renewable source

Disadvantage of photocells

Don't produce electricity when it's too dark or cloudy

A photocell contains two pieces of silicon joined together to make a


...?

P-n junction

The n piece in P-n junction thats made by joining two silicones in photocell is what?

An impurity added to produce an excess of free electrons

The P type silicon which is made by photocell when adding two silicones together to make P-n junction is what?

Has a different impurity than n type silicon added to produce an absence of free electrons

Sunligit contains energy packets called...

Photons

Photons cause what?

Free electrons to move producing an electric current

The output from a photocell depends on what three things ?

* light intensity


* surface area exposes


* distance from light source

The sun is very hot and produces infrared radiation with a very short wavelength. Because of this the glass is.... to this short wavelength radiation


Fill in... .

Glass is transparent to this short wavelength radiation

The sun is very hot and produces infrared radiation with a very short wavelength. What do walls and floor inside a building do with that radiation?

Absorb the radiation, warm unless nd reradiate infrared radiation

The walls and floors are not as hot as the sun and this affects the infrared radiation...how?

The wavelength radiated is longer

When the infrared radiation is radiated by floors and walls causing it to have longer wavelength, what happens when it tries to go via glass?

Glass reflects the longer radiation back inside the building

Why are solar reflectors moved by computer?

To ensure they always face the sun

Remember

Adv of wind turbines?

Don't contribute to global warming as doesn't produce pollution

Wind turbines disadvs (3)?

Take a lot of space.


Spoil the view


Noisy

The current from a dynamo can be increased by what three things?

* using stronger magnet


* increasing number if turns on the coil


*.rotating the magnet faster

The output from a dynamo can be display on an....?

Oscilloscope

What does oscilloscope trace show?

How current produced by the dynamo varies with time

The time for one complete cycle is called..?

The period of the alternating current

A simple generator consists of what?

Coil of wire rotating between the poles of a magnet.

Remember

Power station


How does the process go to generate electricity?

Water boils or burn fossil fuels to boil water to produce steam



Steam at high pressure will turn the turbine



The turbine drives the generator

Tip

Most wavelengths of electromagnetic radiation can pass via the earths atmosphere but infrared radiation is absorbed

Carbon dioxide occurs naturally in the atmosphere as a result of what 5 things?

•…• natural forest fires


•…• volcanic eruptions


•…• decay of dead plant and animal matter


•…•.it's escape from the oceans


•…• respiration

Man made carbon dioxide is caused by... (4)

Burning fossil fuels



Waste incineration



Deforestation



Cement manufacture

Water vapour is the most significant greenhouse gas because....

Almost all water vapour occurs naturally



A mere 0.001% comes from human activity


How is methane produced (naturally and usual way)?

When organic matter decomposes in an environment lacking oxygen

Natural sources where methane is produced?

Wetlands, termites and oceans

Man made sources of methane being produced? (4)

Cattle, rice paddies, burning fossil fuels and burying waste in landfill

How do greenhouse cause global warming?

When radiation from sun goes to earth, it is absorbed by and warms the earth. The earth then reradiates the energy as infrared radiation with a longer wavelength. This longer wavelength radiation is absorbed by the greenhouse gases which warms the atmosphere = global warming

What causes global cooling?

Dust in the atmosphere

Global warming. How do factories contribute to it?

Smoke from factories reflect radiation from the town back to earth

Global cooling. How does ash cloud from volcano contribute to it?

Reflects radiation from sun back into space

Why is electricity cheaper at night?

Because less is needed during might but it still has to be produced

The choice of energy sources depends on what 4 factors?

Availability, ease of extraction, effect of the environment, associated risks

Why do national grids have transformers to step up voltage as high as 400,000 V?

The high voltage leads to...


* reduced energy loss


* reduced distribution costs


* cheaper electricity for consumers

If atom has same number of electrons and protons, they are...?

Neutral

Ionisation involves gaining or losing electrons. When atoms gain electron, it becomes....

Negatively charged

Ionisation involves gaining or losing electrons. When atoms lose electrons, they become...

Positively charged

Formation of ions can cause chemical reaction that could lead to...?

Changing molecules behaviour


E.g. make DNA production of proteins to change

What are the radiations that come from the nucleus?

Beta, alpha, gamma

Which radiation out of three causes most ionisation?

Alpha

Which radiation out of the three causes the least ionisation?

Gamma

What stops alpha?

Easily absorbed by a sheet of paper

Whats stops gamma?

Thick lead

Which out of three radiations is most penetrating?

Gamma

What stops beta from penetrating?

Few millimetres of aluminium

Experiments can be done to identify each type of radiation from it's penetrating power (gamma, alpha and beta) but what should be taken into account?

Background radiation

Example of where alpha radiation is used.

Smoke alarms

How do smoke alarms work with alpha radiation?

Radiation ionises the oxygen and nitrogen atoms in air causing small electric current occurring. When smoke rises it stops atoms from being ionised, making the alarm receive less current = goes off

Example of where beta radiation is used

Paper rolling mill

Tip

Example of where gamma radiation is used?

Kill bacteria and treat cancer or finding leakage in pipes

Passage of blood and other substances can be traced around the body using what radiation?

Beta or gamma

What is plutonium?

Waste product from nuclear reactors which can be used to make nuclear bombs

Plutonium can be used to make what?

Nuclear bombs

What waste does nuclear reactor produce?

Plutonium

How to get rid of low level radioactive waste?

Bury in landfill sites

How to get rid of high radioactive waste?

Encase it in glass then buried deep underground

Remember

Advs in using nuclear power stations?

No greenhouse gases are made


Doesn't use fossil fuels


Disadvantages in using nuclear power stations?

High maintenance


Costs are high


Risky

What are comets?

Comets are balls of ice and dust in orbit around the Sun

What is meteor made up of?

Grains of dust that burn up as they pass via earths atmosphere.

How do meteors form a tail?

They heat the air (hydrogen) round then which glows = shooting star

Why can't we see black holes?

Because light can't escape it and it's mass is large while size of it is small

Advs of unmanned probes over humans

Can go to places where conditions are dealt to humans



Cost less



No life threatened



No sources needed for it (e.g. food)

Outside spacecraft, humans need to wear special spacesuits. What do they use for eyes?

Dark visor that stops him or her from getting blind

The suit that astronauts wear is...

Pressurised and has supply of oxygen

Disadv of unmanned spacecraft ?

They have to be very reliable because there's no way to repair them if they break down

Remember!

What are asteroids?

Mini planets - rocks that we're meant to form a planet

Whats asteroid belt?

Gravity between Mars and Jupiter

Most orbits are where?

Between mars and Jupiter

Just so you know...

Asteroids are large rocks that were left over from the formation of the solar system

How did all planets form?

When clouds of gas and dust collapsed together due to gravitational forces of attraction

What stopped asteroids forming a planet?

Theory; Jupiter's gravitational force (asteroid belt)

Theory of how moon formed

Tip

as the comet passes close to the sun, the ice melts and solar winds blow the dust into the comets tail which always points away from the sun.

What is a object called when it is near earth?

NEO

Just so you know...

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.

The expanding universe

Almost all of the galaxies are moving away from each other with the further galaxies moving fastest

Galileo observer four moons orbiting Jupiter. This confirmed that not everything orbited the earth and supporter Copernicus's idea that planets orbit the sun. Why people were against this idea?

Religious: earth was at the centre!!


Why is the universe constantly expanding?

As a result of big bang

When a source of light is moving away from an observer, its wavelength appears to be what for us?

Longer

When source of light moves away from us, it appears to have longer wavelength which causes its light that we see to become red. This is called?

Red shift

How do scientist exploit red shifts?

By this info (red shift) they can workout the age of the universe

Life cycle of a star (small star)

1. Protostar


2. Normal life (star)


3. Red giant star


4. White dwarf


5. Black dwarf

Life cycle of a star (big star)

1. Nebula


2. Normal life (star)


3. Red super giant star


4. Supernova


5. If big enough = black hole or IF not big enough = neutron star

Why do small stars shine longer than big stars?

Because although they have less hydrogen , they use it at smaller rate so in bigger stars hydrogen gets used up faster