resistance required practical

• Investigating factors affecting resistance of electrical circuits

  1. Use a battery, ammeter, voltmeter, and wire

  2. Measure current and potential difference to calculate resistance

  3. Vary length of wire and measure resistance
• Resistance of wire


  Directly proportional to length of wire
• Zero error


  • Small resistance reading when length of wire is zero
  • Caused by equipment (difficulty positioning crocodile clips, contact resistance)
  • Needs to be subtracted from all readings
• Heating effects


  • Temperature increase causes resistance to increase
  • Use low potential difference to reduce current and heating
  • Only turn on current when taking readings
• Variable resistor


  • Contains a long piece of wire in a coil
  • Slider changes length of wire in circuit to control potential difference