Potential Divider

Potential Divider is a free interactive simulation for GCSE Physics (Edexcel IGCSE 4PH1). Students vary the ratio of two resistances and the supply voltage and measure the output voltage to investigate how a potential divider splits voltage, including LDR and thermistor examples. No login required — includes a self-marking quiz.

Aim: To investigate how a potential divider splits voltage between two resistors.

POWER SUPPLY
V
+
−
I = 3.00 mA
R₁ — Fixed resistor
1000 Ω
R₂ — Fixed resistor
1000 Ω
VOLTMETER V₁
V
V
VOLTMETER Vout
V
V

Results table

Vs (V) R1 (Ω) R2 (Ω) V1 (V) Vout (V) I (mA) Action

Part A — How does the resistance ratio affect the split?

  1. Set the supply voltage Vs to 6.0 V. Leave R2 as a Fixed resistor, set R1 and R2 to 1000 Ω each, and click Record reading.
  2. Increase R1 to 5000 Ω while keeping R2 at 1000 Ω. Record another reading. What happened to Vout as R1 became much larger than R2?
  3. Set R1 back to 1000 Ω and increase R2 to 5000 Ω instead. Record a third reading and compare it with the first two.
  4. Look down your table: how does the ratio R1 : R2 compare with the ratio V1 : Vout? Check that V1 + Vout always adds up to Vs.

Part B — Using the LDR and thermistor

  1. Change the component for R2 to Light-dependent resistor (LDR). Drag the light intensity slider to 100% (bright) and record a reading, then drag it to 0% (dark) and record again.
  2. Change the component for R2 to Thermistor (NTC). Record a reading at a low temperature (around 0 °C) and another at a high temperature (around 80 °C).
  3. Compare your LDR and thermistor rows with your Part A rows. Explain why Vout changes the way it does as the light dims or the temperature rises, linking your answer to how each component's resistance responds to its environment.