P2 OCR Gateway Science GCSE Physics

My notes I made for my exam which I re-sited so these notes are quite detailed because I knew I had to do better (which I did :D ) but some may be brief because I could remember the section :) Hope it helps!!

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  • Created by: Lucy :)
  • Created on: 11-03-13 22:34
Preview of P2 OCR Gateway Science GCSE Physics

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Using the Sun's Energy
Photocells: direct current (DC) ­ flows same way round
^ made of silicon - a semiconductor
^ silicon atoms absorb some of the energy ­ knocking loose some electrons
^ electrons then flow around circuit = electricity
Current + power output depend on:
Surface area ­ bigger = more electricity
Intensity of light ­ brighter light = more electricity
Distance from light source ­ closer cell = more intense light hitting it will be
Advantages:
No moving parts = sturdy, low maintenance + long lasting
No power cables or fuel
Solar power won't run out ­ renewable source
^ doesn't pollute environment
Disadvantages:
No sunlight = no power ­ night and bad weather = not good!
Curved mirrors:
^ concentrate energy from the sun
E.g. solar oven (single curved mirror) or generate steam to produce electricity (large
curved mirrors or many small)
Most efficient if track Sun's movement
Passive Solar Heating
Energy from Sun used to heat something directly
Glass lets in heat + light from Sun ­ is absorbed by things in room = heating them up
Light from Sun has short wavelength = pass through glass
Heated things in room emit IR ­ longer wavelength = can't escape through glass =
reflected back into room
^ `greenhouse effect' works to heat and keep heat inside a building
Solar water heaters use this ­ light absorbed by the black pipes = heats water
Wind Power
Energy from Sun heats atmosphere = convection currents ­ which produce wind
Wind turbines convert kinetic energy of moving air into electricity
Advantages Disadvantages
Cheap to run ­ tough + reliable, wind is free 1500 wind turbines = 1 coal-fired power station
Doesn't produce polluting waste Spoil view (visual pollution), blades = noise pollution
Renewable ­ wind never going to run out Wind not always fast enough to generate power
Impossible to increase supply when extra demand
Hard to find place to build ­ spaced out + windy place
Expensive to set up wind farm ­ especially out at sea
Producing Electricity
Power Advantages Disadvantages
Source

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Fossil Fuels Concentrated source (little bit Burning them causes acid rain + produces CO2
of coal = lot of heat) Buy most from other countries = no control of
At moment readily available price + supply
Sources are running out
Biomass Renewable burning methane produces CO2 but
`carbon neutral' plants took need a lot to replace 1 lump of coal
CO2 when growing a lot of room to grow
Don't need to import straw
and manure from other
countries
Nuclear stations can produce lots of…read more

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The Dynamo Effect = usingto transform KE into electrical energy
ELECTROMAGNETIC INDUCTION: The creation of a VOLTAGE (and maybe current) in a wire
which is experiencing a CHANGE IN MAGNETIC FIELD
Situation when get EM induction = electrical conductor moves through magnetic field +
magnetic field through electrical conductor changes
Get a bigger voltage + current increase: strength of magnet, no.…read more

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The Greenhouse Effect
Concentration of greenhouse gases in atmosphere increasing as sources are increasing:
Carbon Dioxide: people use more energy (cars) ­ get from burning fossil fuels which
releases CO2
^ more land is needed for houses + food = space made chopping + burning trees ­ fewer
trees = less CO2 absorbed + burning releases more CO2
^ also comes from natural sources (respiration + volcanic eruptions)
Methane: Cattle farming increased to feed growing population = methane increase
^ decaying waste in landfill increasing…read more

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­ radioactive substance mustn't decay too quickly ­
beta penetrates through paper and card but not too much
Gamma: Medical (high doses kill living cells (kills cancer), kill microbes = sterilising)+
industrial (non-destructive testing ­ planes direct gamma at turbine blades in engines,
too much gets through = crack or fault with welding)
Nuclear Power
Nuclear fission ­ atoms in nuclear fuel split in 2 = lots of heat released, water used as
coolant to take away heat produced ­ heat used to produce steam…read more

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Earth
Calculate object's trajectory (it's path)
Difficult to spot ­ small, dark, unusual orbits
Small = burn up in atmosphere
Large = explosions more powerful than nuclear weapons
If explode a bomb on or in it then might nudge it off course
Moon: heat of collision dense iron cores merged to form Earth's core ­ less dense was
ejected really hot dust + rocks = orbited Earth then eventually formed Moon
Evidence: Moon lower density than Earth + not big iron core
^ Moon rocks…read more

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More distant galaxies = greater red-shift = moving away quicker than lost closer = whole
Universe is expanding
Cosmic background radiation = low frequency microwave radiation from Universe
^ as Universe expands and cools, background radiation `cools' + drops frequency
Big Bang: All squashed together, `exploded' ­ still expanding
Life Cycle of Stars
Clouds of dust and gas
Force of gravity = ^ spiral together = Protostar ­ gravitational energy ­ converted to heat
energy = temp increase
Main Sequence Star ­ temp high, hydrogen…read more

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