P8.2c recall that, in the national grid, electrical SP13b 176 power is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic use P8.2d recall that step-up and step-down SP13b 176 transformers are used to change the potential difference as power is transferred from power stations P8.2e explain how the national grid is an efficient SP13b 176 way to transfer energy P8.2f link the potential differences and SP13c 178-179  numbers of turns of a transformer to the power transfer involved; relate this to the advantages of power transmission at high voltages P8.2g recall that the domestic supply in the UK is SP10h 157 a.c. at 50Hz and about 230 volts P8.2h explain the difference between direct and SP10h 157 alternating voltage P8.2i recall the differences in function between SP10i 158 the live, neutral and earth mains wires, and the potential differences between these wires P8.2j explain that a live wire may be dangerous SP10i 158-159 even when a switch in a mains circuit is open, and explain the dangers of providing any connection between the live wire and earth PM8.2i apply: potential difference across primary SP13c 178 coil (V) x current in primary coil (A) = potential difference across secondary coil (V) x current in secondary coil (A) P8.3 Beyond Earth P8.3a explain the red-shift of light as seen from SP7d and e 124-127  galaxies which are receding (qualitative only). The change with distance of each speed is galaxy’s evidence of an expanding universe P8.3b explain how red-shift and other evidence SP7e 126-127  can be linked to the Big Bang model P8.3c recall that our Sun was formed from dust SP7c 122-123  and gas drawn together by gravity and explain how this caused fusion reactions, leading to equilibrium between gravitational collapse and expansion due to the energy released during fusion
P8.2c recall that, in the national grid, electrical power is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic use SP13b 176 P8.2d recall that step-up and step-down transformers are used to change the potential difference as power is transferred from power stations SP13b 176 P8.2e explain how the national grid is an efficient way to transfer energy SP13b 176 P8.2f  link the potential differences and numbers of turns of a transformer to the power transfer involved; relate this to the advantages of power transmission at high voltages SP13c 178-179 P8.2g recall that the domestic supply in the UK is a.c. at 50Hz and about 230 volts SP10h 157 P8.2h explain the difference between direct and alternating voltage SP10h 157 P8.2i recall the differences in function between the live, neutral and earth mains wires, and the potential differences between these wires SP10i 158 P8.2j explain that a live wire may be dangerous even when a switch in a mains circuit is open, and explain the dangers of providing any connection between the live wire and earth SP10i 158-159 PM8.2i apply: potential difference across primary coil (V) x current in primary coil (A) = potential difference across secondary coil (V) x current in secondary coil (A) SP13c 178 P8.3 Beyond Earth P8.3a  explain the red-shift of light as seen from galaxies which are receding (qualitative only). The change with distance of each galaxy’s speed is evidence of an expanding universe SP7d and e 124-127 P8.3b  explain how red-shift and other evidence can be linked to the Big Bang model SP7e 126-127 P8.3c  recall that our Sun was formed from dust and gas drawn together by gravity and explain how this caused fusion reactions, leading to equilibrium between gravitational collapse and expansion due to the energy released during fusion SP7c 122-123