Wheatstone Bridge: Conductivity Measurement

Conductivity Measurement via Wheatstone Bridge

Balance the bridge to find the resistance (and conductivity) of the electrolyte solution.

Conductivity Cell (Unknown Rₓ)

Electrolyte Solution 0.01 M KCl (Low Conductivity) 0.1 M KCl (Medium Conductivity) 1.0 M KCl (High Conductivity)

Electrode Distance (l) 1.0 cm

Electrode Area (A) 1.0 cm²

Cell Constant (G* = l / A) 1.00 cm⁻¹

Bridge Controls

Variable Resistor (R₂) 50.0 Ω

Galvanometer / Null Detector

0.00 mA

Bridge is Unbalanced

Calculated Rₓ -- Ω

Conductivity (κ) -- S/cm

How it works:

1. An AC power source (Oscillator, O) is used in the range of 500-5000 Hz to prevent electrolysis (polarization) of the solution.
2. Because AC is used, a standard galvanometer cannot detect the null point. Instead, an earphone or a magical "null detector" (P) is used.
3. Adjust R₂ until the detector shows zero current. At this balance point: R₁/R₂ = R₃/Rₓ ➔ Rₓ = (R₁ × R₃)/R₂ (Assuming R₃ is the unknown). *Note: In this sim, Rₓ is in the arm opposite R₂ for standard visual layout, so Rₓ = R₂ × (R₄/R₃) where R₃ = R₄ = 100 Ω.*
4. Once Rₓ is known, Conductivity κ = Cell Constant (G*) / Rₓ.

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