2.1.10 Required Practical: Investigating I–V Characteristics

• Equipment Needed

  • Power supply (variable voltage)
  • Ammeter
  • Voltmeter
  • Component under test (resistor, filament lamp, diode, etc.)
  • Connecting wires
  • Variable resistor (rheostat)
  • Switch (optional, for safety)
• Safety Precautions

  Ensure all equipment is in good condition and properly connected<|>Avoid touching live wires or components when the circuit is powered<|>Be cautious with high voltages and overheating components
• Setup for a Simple Circuit

  1. Connect the resistor in series with a variable resistor (rheostat), ammeter, and the power supply

  2. Connect the voltmeter in parallel across the resistor to measure the voltage drop

  3. Connect the filament lamp in series with a variable resistor (rheostat), ammeter, and the power supply

  4. Connect the voltmeter in parallel across the lamp to measure the voltage drop

  5. Connect the diode in series with a variable resistor (rheostat), ammeter, and the power supply

  6. Connect the voltmeter in parallel across the diode to measure the voltage drop
• Collect Data

  1. Set the power supply to a low voltage

  2. Adjust the variable resistor to change the current through the resistor

  3. Measure and record the current (I) and voltage (V)

  4. Repeat for a range of voltages

  5. Start with a low voltage and gradually increase it for the filament lamp

  6. Measure and record the current (I) and voltage (V)

  7. Start with zero voltage and increase the voltage in the forward direction for the diode

  8. Reverse the voltage to measure the behavior in reverse bias
• Plot the I-V Characteristics


  1. Plot the current (I) on the y-axis and the voltage (V) on the x-axis

  2. For each component, observe the shape of the graph
• Resistor

  • Shows a straight line through the origin, indicating a linear relationship (Ohm’s Law: V=I×R)
• Filament Lamp

  • The graph curves upwards, showing a non-linear relationship due to increasing resistance with temperature
• Diode


  • Shows very little current until a certain forward voltage (threshold) is reached, after which current increases rapidly; in reverse bias, the current should be minimal until breakdown occurs
• Analyze the Results

  1. The straight line through the origin confirms Ohm’s Law and indicates constant resistance for the resistor

  2. The curve demonstrates that resistance increases with temperature for the filament lamp

  3. In forward bias, the diode conducts only after reaching a threshold voltage; in reverse bias, it ideally conducts no current until breakdown
• This practical investigation allows students to visually understand and analyze the electrical properties of various components
• By measuring and plotting the I-V characteristics, you gain insights into how components like resistors, filament lamps, and diodes respond to changes in voltage
• This understanding is fundamental for circuit design and analysis in both theoretical and practical contexts