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Wheatstone bridge

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Objective

Balance a bridge: the meter reads zero when R1/R2 = R3/Rx.

Procedure

  1. Run: the voltmeter reads 0 V (balanced).
  2. Change R4 to 2.4 kΩ and observe the unbalance voltage.

Theory

Balance condition R1/R2 = R3/R4. With 1 kΩ, 1 kΩ and 2.2 kΩ the unknown R4 = 2.2 kΩ gives 0 V; detuning R4 to 2.4 kΩ gives about 0.1 V from a 5 V supply.

Questions to answer

  1. How would you use this to measure an unknown resistor?

Components used

Battery / DC source, Panel voltmeter, 4 × Resistor 220 ohm 1/4W

About the model

Ideal wires; component models as listed in the catalogue (no parasitics, no temperature drift). Built without a breadboard so the schematic stays readable.

Open this experiment in the circuit simulator

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