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  • Created by: niki
  • Created on: 12-04-11 14:51

> energy transferred (kilowatt-hours, kWh) = power of device (kilowatts, kW) X time in use (hours, h)

> total cost = number of kWh used X cost per kWh

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using electrical energy

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> the national grid is a network of cables and transformers

> we use step-up transformers to step up the power stations' voltages to the grid voltage

> we use step-down transformers to step the grid voltage down for use in our homes

> a high grid voltage reduces energy loss and makes the system more efficient

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the national grid

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> electricity generators in power stations are driven by turbines

> much more energy is released per kilogram from uranium then from fossil fuels

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fuel for electricity

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> a wind turbine is an electricty generator on top of a tall tower

> a wave generator is a floating generator turned by the waves

> hydroelectricty generators are turned by water running downhill

> a tidal power station traps each high tide and uses it to turn generators.

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energy from wind and water

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> we can convert solar energy into electricty using solar cells or use it to heat water directly in solar heating panels

> geothermal energy comes from the energy released by radioactive substances deep inside the earth

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power from the sun and the earth

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> fossil fuels produce greenhouse gases

> nuclear fuels produce radiactive waste

> renewable energy resources can affect plant and animal life

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energy and the environment

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> the electromagnetic soectrum ( in order of increasing wavelength) is:

  • gamma rays and x rays
  • ultraviolet
  • violet
  • indigo
  • blue
  • green
  • yellow
  • orange
  • red
  • infra red
  • microwaves
  • radio waves

> all electromagnetic waves travel through space at a speed of 300 million m/s

>wave speed= wavelength X frequency

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the electromagnetic spectrum

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> x-rays and gamma radiation are absorbed by dense materials such as bone and metal

> x-rays and gamma radiation damage living tissue when they pass through it

> x-rays ar used in hospitals to take radiographs

> gamma rays are used to kill harmful bacteria in food, to sterilise surgical equipment and to kill caner cells

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gamma rays and x-rays

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> ultraviolet radiation is in the electromagnetic spectrum between violet light and x-radiation

> ultraviolet radiation has a shorter wavelength than light

> ultraviolet radiation harms the skin and the eyes

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light and ultraviolet radiation

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> the use we make of radio waves depends on the frequency of the waves

> visible light and infra red radiation are sued to carry signals in optical fibres

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> analogue signals vary continuously in amplitude

> digital signals are either high ('1') or low ('0')

> digital transmission, when compared with analogue transmission, is free of noise and distoration. It can also carry much more information

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analogue and digital signals

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> a radioactive substance contains unstable nuclei

> an unstable nucleus becomes stable by emitting radiation

> there are 3 types of radiation from radioactive substances

  • alpha radiation
  • beta radiation
  • gamma radiation

> radioactive decay is a random event- we cannot predict or influence when it will happen

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observing nuclear radiation

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> alpha radiation is stopped by paper or a few centimetres of air

> beta radiation is stopped by thin metal or about a metre of air

> gamma radiation is stopped by thick lead and has an unlimited range of air

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alpha, beta and gamma radiation

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> the half-lite of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to halve

> the number of unstable atoms and the activity decreases to half in one half-lite

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> the use we can make of a radioactive substance depends on

  • its half-lite
  • the type of radiation it gives out
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radioactivity at work

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> light from a distant galaxy is red-shifted to longer wavelengths

> the most distant galaxies are about 13,000 million light years away

> the universe is expanding

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the expanding univers

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> the universe started with the Big Bang, a massive explosion from a very small point

> background microwave radiation is radiation created just after the big bang

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the big bang

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> the earth's atmosphere absorbs all eceltromagnetic waves (except visible light, radio waves and some ultraviolet radiation)

> satellite detectors are used to make observations outside the visible and the radio spectrum

> we also get clearer images from telescopes on satellites detecting visible light

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looking into space

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