unit 1, 2 and 3

• ways of energy transfer

  • mechanically
  • electrically
  • heating
  • radiation
• specific heat capacity is the energy required to increase 1kg of a material by 1 degrees Celsius
• mains electricity is an alternating current supply where the current changes direction. this has a frequency of 50Hz and around 230V. Direct current flows in the same direction and is found in batteries and AC supplies, that have passed through a diode.
• the live wire is brown and is 230V. The neutral wire is blue and completes the circuit with 230V. The earth wire is brown and yellow and is the safety wire with 0V
• The national grid is a system of cables and transformers linking power stations to peoples homes/buildings. Transformers increase and decrease the voltage. step up transformers increase the voltage and reduce the current to reduce energy lost through the heating of the wire. Step down transformers decrease voltage and increase current to bring back down to a safer potential difference
• the specific heat of fusion is the energy required to change 1kg of a solid into a liquid.
• specific latent heat is the energy required to change state of 1kg of a substance with no change in temperature
• 1901- JJ Thompson suggested the plum pudding model of the atom. It was made up of a ball of positive charge with negative particles embedded inside.
• 1909 - Rutherford performed the alpha scattering/gold foil experiment. During this positive alpha particles were shot at a thin sheet of gold foil. Most went straight through, some deflected and a few bounced straight back. From this he concluded that mass is concentrated in the nucleus, the atom is mostly empty space and that the nucleus is positively charged.
• the half life of a radioactive substance is the time taken for the number of radioactive nuclei to halve
• fission:

  • large radioactive atoms split in half due to being unstable
  • A huge amount of energy is then released
  • Neutrons are released and split more atoms causing a chain reaction
  • Control rods absorb neutrons to reduce the amount of fissions to a manageable amount
• fusion:

  • small nuclei are fused together under heat and pressure
  • the nuclei are both positively charged and therefor repel each other making it harder to fuse them together
  • A huge amount of energy is released (more energy than fission)
  • no radioactive waste is produced
• contamination is the unwanted presence of radioactive atoms on a material. irradiation is exposing an object to radiation but the object does not become radioactive.