Exam Qs

• Explain why the total positive charge in every atom of an element is always the same


  positive charge is provided by protons

  (every atom of the same element contain the) same number of protons
• Plan an experiment that would allow the student to determine the density of the object.


  • measure mass

  • use a top pan balance or scales

  • part fill a measuring cylinder with water

  • measure initial volume

  • place object in water

  • measure final volume

  • volume of object = final volume − initial volume

  • fill a displacement / eureka can with water

  • water level with spout

  • place object in water

  • collect displaced water

  • measuring cylinder used to determine volume of displaced water
• What is the equation for uncertainty?


  Range of values/2
• It could be dangerous if the temperature of the air inside the canister increased by a large amount.


  (if the temperature increases) the pressure increases so it could explode
• 1,000,000 Joules in 1 mega joule
• What is the correct way to connect the ammeter and the voltmeter into the circuit?


  ammeter in series with the resistor, voltmeter in parallel with the resistor
• Explain how the motion of the air molecules caused the pressure in the container to change as the temperature decreased.


  pressure decreased because molecules have less (kinetic) energy so fewer collisions (with the wall/container each second)
• Explain the difference between direct and alternating potential difference.


  direct potential difference is always in the same direction alternating potential difference changes direction
• The cable used to connect the car to the mains electricity supply has a low resistance. Explain why it is better to use a cable with a low resistance than to use a cable with a high resistance.


  lower potential difference across the cable it is more efficient
• The student increased the temperature of the thermistor. Explain how the current in the thermistor changed.


  the current increased (because) the resistance (of the thermistor) decreased
• The heating element of the kettle was connected to the mains supply. Explain why the temperature of the heating element increased.


  electrons collide with particles in the heating element which increases the (kinetic) energy of the particles (in the heating element)
• Why is it difficult to detect gamma radiation?


  gamma radiation is only weakly ionising
• The teacher investigated how the thickness of lead affected the amount of gamma radiation that could pass through it.Explain why the teacher stood as far away from the apparatus as possible


  to reduce the amount of radiation received because radiation increases the risk of cancer or (genetic) mutation
• What happens to an atom when it is ionised by an alpha particle?


  the atom becomes a positive ion

  the atom loses an electron
• The battery can be charged by either the wind turbine or the generator. Give two reasons why this is useful.


  sometimes there is no wind (but the battery can still be charged using the generator)

  when there is wind less fuel is burned
• Describe how the student could use a displacement method to determine an accurate value for the volume of a single coin.


  add several coins to the measuring cylinder measure the change in the water level in the measuring cylinder divide by the number of coins added