Investigating I-V Graphs

Investigating I-V Graphs is a free interactive simulation for GCSE Physics (Edexcel IGCSE 4PH1). Students plot and compare I-V graphs for a fixed resistor, a filament lamp and a diode to investigate how current varies with voltage for each component. This is a required practical for Edexcel IGCSE 4PH1. No login required — includes a self-marking quiz.

Aim: To investigate the current-voltage characteristics of a fixed resistor, a filament lamp and a diode.

POWER PACK
AMMETER
A
A
Fixed Resistor
VOLTMETER
V
V

Results table

Component Voltage (V) Current (A) Action

Part A — The fixed resistor

  1. Select the Resistor and turn the power pack dial (or drag the slider) to set the voltage to 0 V. Read the voltmeter and ammeter.
  2. Record the voltage and current in the table, then increase the voltage in steps of about 1 V up to +6 V, recording a row each time.
  3. Now do the same for negative voltages, down to -6 V, recording a row at each step.
  4. Plot a graph of current (y-axis) against voltage (x-axis) for the resistor. What shape is the graph, and what does this tell you about the resistor's resistance as the voltage changes?

Part B — The filament lamp

  1. Select the Filament Lamp and repeat the process from Part A: step the voltage from -6 V to +6 V, recording the voltmeter and ammeter readings in the table each time.
  2. Watch how brightly the lamp glows at low voltages compared with high voltages.
  3. Plot the lamp's I-V graph. How does its shape differ from the resistor's straight line, and what does this suggest is happening to the filament's resistance as the current increases?

Part C — The diode

  1. Select the Diode and step the voltage from -6 V up to +6 V in small steps (try 0.5 V steps near 0 V), recording each pair of readings.
  2. Notice the voltage at which the diode suddenly starts to conduct, and what happens to the current when the voltage is negative.
  3. Plot the diode's I-V graph. Comparing all three graphs, which component obeys Ohm's law, and how can you tell just by looking at the shape of its graph?