Current / PD Characteristics

• Investigating the current-voltage characteristics of circuit components

  1. Use a circuit with a battery, resistor, ammeter, variable resistor, and voltmeter

  2. Measure potential difference across resistor and current through resistor

  3. Adjust variable resistor and record new readings

  4. Repeat for a range of readings

  5. Reverse battery direction and repeat measurements
• Current through a resistor

  Directly proportional to potential difference across resistor
• Resistor

  • Ohmic conductor
  • Relationship between current and potential difference remains linear if temperature is kept constant
• Current through a filament lamp

  Not proportional to potential difference
• Filament lamp

  • As current increases, temperature of filament increases, causing resistance to increase
• Investigating current-voltage characteristics of a diode

  1. Use a circuit with a diode, resistor, variable resistor, ammeter, and voltmeter

  2. Measure potential difference and current

  3. Adjust variable resistor and record new readings

  4. Repeat for a range of readings in both forward and reverse battery directions
• Diode

  • Only conducts current when potential difference is around 0.6-0.7V
  • No current flows when potential difference is reversed
• A sensitive ammeter called a milliammeter is used to measure the low currents through a diode