wrong questions

• The resitant of the lamp is directly proportional to the potential difference


  • it is not true
  • resistant increase with potential difference (whatever the data shows )
  • doubling the potential difference does not result in doubling of resistant
• The student use a power supply that had fixed the output voltage settings. Describe how the student could add a component to the circuit that would provide a continuously variable voltage across the lamp

  • variable resistor
  • in series with the lamp
• Explain with a diagram, the method to investigate how the resistant change with the potential difference across the lamp

  • measure current with a ammeter
  • measure potential dfference with a volmeter
• immerse heater has a larger current and is connected to a batter. Kettle has a smaller current and is connected to the main supply. State 2 difference in the movement of charge

  1. chage flow in one direction in heater but 2 direction in kettle
  2. rate of charge is greater in immerse heater than kettle
• Explain why the resistor become warmer

  • As the wire is made up of ion lattice
  • When the charge pass through it collides with the metal ions
  • causing them to vibrate more in fixed position
  • some energy is transferred to thermal energy store
• Explain why a transformer won't work if the current is a direct current?

  • As the current isn't changing direction
  • no changing magnetic field