all topics

HideShow resource information
  • 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

1 of 36




using electrical energy

2 of 36

> 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

3 of 36




the national grid

4 of 36

> electricity generators in power stations are driven by turbines

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

5 of 36




fuel for electricity

6 of 36

> 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.

7 of 36




energy from wind and water

8 of 36

> 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

9 of 36




power from the sun and the earth

10 of 36

> fossil fuels produce greenhouse gases

> nuclear fuels produce radiactive waste

> renewable energy resources can affect plant and animal life

11 of 36




energy and the environment

12 of 36

> 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

13 of 36




the electromagnetic spectrum

14 of 36

> 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

15 of 36




gamma rays and x-rays

16 of 36

> 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

17 of 36




light and ultraviolet radiation

18 of 36

> 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

19 of 36





20 of 36

> 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

21 of 36




analogue and digital signals

22 of 36

> 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

23 of 36




observing nuclear radiation

24 of 36

> 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

25 of 36




alpha, beta and gamma radiation

26 of 36

> 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

27 of 36





28 of 36

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

  • its half-lite
  • the type of radiation it gives out
29 of 36




radioactivity at work

30 of 36

> 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

31 of 36




the expanding univers

32 of 36

> 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

33 of 36




the big bang

34 of 36

> 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

35 of 36




looking into space

36 of 36


No comments have yet been made

Similar Physics resources:

See all Physics resources »