physics

• Life cycle of stars similar mass to Sun

  1. Nebula - clouds of dust and gas pulled together by gravitational forces
  2. Main sequence - stable state, hydrogen converted to helium, nuclear fusion - huge amounts of heat and light produced, continues for many millions of years
  3. Red giant - hydrogen runs out, star expands, gets colder, uses up all helium, outward forces decrease
  4. White Dwarf - eventually collapses due to own gravity, becomes much smaller and very dense
• Explain how the graphite core and the movable rods are used to maintain and control the chain reaction

  • neutrons released in chain reaction
  • slower neutrons needed for fission
  • some neutrons are too fast
  • control rods can be moved in and out
  • control rods control speed of reaction
  • graphite core is the moderator
  • graphite core slows down neutrons
  • moveable rods absorb neutrons
  • moveable rods make more or fewer neutrons available for fission