wrong answers

• a negatively charged student touches a metal tap and receives an electric shock. explain why.

  there is potential difference between the person and the tap. electrons transfer from the person to the earth
• some carpets have thin copper wires running through them. suggest why the student is less likely to receive an electric shock after walking on the carpet

  • good conductor
  • low resistance
  • charge doesn't build
• a fuel used in nuclear power stations

  uranium
• describe the effect on power output when the wind speed is halved if the power output of the turbine is directly proportional to the kinetic energy of the air passing the blades each second

  • mass of air passing the turbine blades is halved which decreases kinetic energy by a factor of two
  • (wind speed is halved) decreasing kinetic energy by a factor of four
  • so kinetic energy decreases by a factor of eight
• explain how oiling would effect the efficiency of a wind turbine

  efficiency would increase --> percentage/ proportion of energy produced increases --> less friction
• what does taking the measurements more than once improve the accuracy of the density value (density of rock practical)

  • a mean can be calculated
  • reduces/ identifies anomalies
  • reduces effect of random errors
• what is the resolution of a thermometer

  the smallest value it can measure e.g. 27.9 has a resolution of 0.1
• 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 negatively charged
  • electrons transferred from the cloth to the rod
  • more positive charge on the cloth than negative charge
• a negatively charged rod is held near an earthed conductor. explain why a spark jumps between the negatively charged rod and the earthed conductor

  large potential difference between the 2 objects --> causes negative electrons/ charges to move through the air from rod to conuctor
• why is step up transformer used in the national grid

  increases the voltage and decreases the current so it is easier and quicker and easier to transport. it makes sure that the electricity can be transported in large quantities with high efficiency, reducing thermal energy transfer
• what does an alpha particle consist of

  2 protons and 2 electrons
• explain how the risk from internal contamination is different to the risk from external irritation by a source of alpha radiation

  • internal contamination can cause internal burns
  • it is ionising
  • external radiation causes mild skin burns as it is stopped by the skin
  • it is low penetrating
• what is electrical current?

  amount of electrons flowing in a wire in a circuit
• Describe how static charge(static electricity)can build up on an object

  Friction between2 objects can cause e- to move from object to another. If insulators charges e- remain on object (static)both will be charged
• What is potential difference( Voltage)

  difference in charge that 'pushes' e- around the circuit
• What is resistance

  Opposition faced against current
• What is a series circuit

  Everything included in 1 singular circuit- circuit in one path
• What is a parallel circuit

  separate side circuit attached to a main circuit- circuit with more than one path
• Write down the laws for series and parallel circuits

  Series- current same no matter where you measure

  Parallel- current divided between branches in a circuit
• Write down the voltage laws of series and parallel circuits

  Series- voltage will divide between the components in circuit

  Parallel- each branch receives same voltage. Current is directly proportional to voltage (if temperature remains constant)