corrections to give me a 9

• why is a step up transformer used in the national grid?

  • it increases potential difference
  • decreases current
  • reduces thermal energy transfer to its surroundings
  • increases efficiency
• why is a step down transformer used in the national grid?

  • decreases potential difference while increasing increasing current
  • it makes it safer value for consumers
• what is the difference between a step up transformer and step down transformer?


  step up transformer has more turns on the secondary coil than the primary coil

  its the opposite for a step down transformer
• Explain why a spark jumps between a negatively charged rod and an earthed conductor?

  • there is a large potential difference between the two objects
  • negative electrons move through the air from the negativity charged rod to the conductor
• why does the reading on a balance increase when someone is holding an object?

  • there is additional downwards force which increases the mass
  • the held object is negatively charged
  • like charges repel
• a student rubbed a plastic rod with a cloth, the rod became negatively charged and the cloth became positively charged

  explain why the cloth became positively charged?

  • electrons are transferred from the rod to the cloth
  • electrons are negatively charged
  • there are more positive charges than negative charges on the cloth
• explain why people should be encouraged to use energy efficient electrical devices?

  • more energy efficient devices waste less energy
  • causes lesss harm to the environment
• explain how oiling mechanical parts of a wind turbine would affect the efficiency?

  • the efficiency of the wind turbine would increase
  • less work is done
  • the percentage amount of energy wasted would decrease
• suggest reasons why wind power cannot meet high demands?

  • the amount of electricity generated depends on the strength of the wind
  • wind is unreliable
• explain how the risk from internal contamination is different to the risk from external irradiation by a source of alpha radiation?

  • alpha radiation has a low penetrating ability
  • alpha radiation is stopped by the skin
  • internally alpha radiation is absorbed by organs
  • alpha radiation is highly ionising
  • internal radiation causes greater risk of harm to organs
• describe a method that can be used to determine the density of an irregular object?

  1. for this experiment you will need; scale, beaker, eureka can and a measuring cylinder
  2. fill your eureka can with water until it meets the with the spout
  3. place your eureka can in a tray and place your beaker beside it
  4. submerge your irregular object in water until it reaches the base of your eureka can
  5. you will see water displace into your beaker
  6. pour your displaced water into your measuring cylinder which will give you the volume
  7. find the mass of your irregular object on a scale
  8. density= mass / volume