P2

P2

1. Energy from the Sun.

   • Kinetic energy from moving air turns the blades on a wind turbine to produce electricity.
   • Some gases in the Earth's atmosphere trap heat from the Sun increasing global warming.Scientists disagree about how much effect humans have on the increase in levels of these Greenhouse gases.
   • Passive solar heating uses glass to help keep buildings warm.
   • Photocells do not need fuel or cables,need little maintenance and cause no pollution.

2. Electricity generation.

   • Power = Voltage x Current.
   • In power stations fuels release energy as heat.Water is heated to produce steam.The steam drives turbines.Turbines turn generators.Generators produce electricity. Efficiency = Output \ Total energy input x 100%.
   • Energy = Power x Time.
     • Nuclear fuels are radioactive.The radiation produced can cause cancer.Waste products remain radioactive for a long time.
       • The main forms of ionising radiation are alpha,beta and gamma.Their uses depend on their penetrative and ionisation properties.
   • A dynamo produces electricity when coils of wire rotate inside a magnetic field.The size of the current depends on the number of turns,the strength of the field and the speed of rotation.
   • Transformers change the size of the voltage and current.The National Grid transmits electricity around the country at high voltage and low current.This reduces energy loss.

3. Our Solar System.

   • Planets,asteroids and comets orbit the Sun in our Solar System.
   • When two planets collide,a new planet and a moon may be formed.
   • Medium-sized stars,such as our Sun,were formed from nebulae and will eventually become red giants,white dwarfs and finally black dwarfs.

4. The Universe.

   • Scientists believe that the Universe started with a Big Bang.
   • The Universe is explored by telescopes on Earth and in space.Large distances mean that it takes a long time for information to be received and makes inter-galactic travel unlikely.
   • The Universe consists of many galaxies.Models of the Universe have changed over time and sometimes these changes take a long time to be accepted.
   • Most asteroids are between Mars and Jupiter but some pass closer to Earth.They are constantly being monitored.An asteroid strike could cause climate change and species extinction.