Tricky Circuit

10 kΩ

A knob becomes a voltage

Move a contact along a resistance track and set the output voltage.

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10 kΩ · Potentiometer
Potentiometer / wiper. A potentiometer is a three-terminal variable resistor. Its moving contact is the wiper. Here it divides a 10 kΩ track into R1 above and R2 below.
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EXPERIMENT BENCH

Change the circuit settings, predict the readings, then check a challenge. These are learning models, with the assumptions explained in each lesson.

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A knob becomes a voltage

Linear 10 kΩ potentiometer, unloaded output. Real loads change the output.

Vout = 5 × position/100. R1 + R2 stays 10 kΩ, so supply current stays 0.5 mA. Turning the knob changes the ratio, not the total resistance.

Difficulty

  1. Build · A knob becomes a voltage

    Power on and place the wiper at 50%. Reach 2.50 V.

    Need a hint?

    50% → 2.50 V

  2. Explore · A knob becomes a voltage

    Move the wiper to 0%. Check that the output reaches 0 V.

    Need a hint?

    0% → 0 V

  3. Solve it · A knob becomes a voltage

    Set the output to 3.30 V. Find the correct wiper position.

    Need a hint?

    66% → 3.30 V

Extra reading and circuit recipes

A knob becomes a voltage

The knob moves a contact

The wiper is the moving contact of a potentiometer, a three-terminal variable resistor. It divides one track into two sections. In this linear 10 kΩ model, halfway along the track gives half the supply voltage.

A voltage setting is not a power supply

The output here is unloaded: nothing draws current from the wiper. Connecting a load changes the effective lower resistance and can lower the voltage. A buffer, a circuit that follows the voltage while drawing little input current, can reduce this effect.

When the wiper moves from 25% to 75%, what happens to current drawn by the unloaded 10 kΩ track?

  1. It increases
  2. It decreases
  3. It stays the same
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The full track stays 10 kΩ, so the supply current remains 5 V / 10 kΩ = 0.5 mA. Only the output ratio changes: 1.25 V becomes 3.75 V.

Find two voltage settings

Power on. Find positions that give 1.00 V and 4.00 V: 20% and 80%. At both settings, check that the two displayed track resistances still add to 10 kΩ.