required practical 4

• Investigating the current-voltage characteristics of circuit components

  1. Use a voltmeter to read the potential difference across the component

  2. Use an ammeter to read the current through the component

  3. Adjust a variable resistor and record the new readings

  4. Repeat for a range of readings

  5. Switch the direction of the battery and repeat the readings
• For a resistor


  The current is directly proportional to the potential difference
• A resistor is an ohmic conductor
• If the temperature of the resistor increases, the graph will not have a straight line passing through the origin
• For a filament lamp

  The current is not proportional to the potential difference
• Investigating the current-voltage characteristics of a diode

  1. Use a milliammeter to measure the low current

  2. Adjust a variable resistor and record the potential difference and current

  3. Repeat for a range of readings

  4. Switch the direction of the battery and repeat the readings
• Diode


  • Only allows current to flow in one direction
  • Requires a potential difference of around 0.6-0.7 V before current starts to flow
  • Has a high resistance in the reverse direction
• You will find plenty of questions on this required practical in the revision workbook