Meter Bridge and Potentiometer

Also called

meter bridge · metre bridge · Wheatstone bridge · null point · balance point · jockey · galvanometer · unknown resistance · resistance box · potentiometer · comparing EMFs · internal resistance of a cell · balancing length · potential gradient · slide wire bridge · null method · मीटर सेतु · व्हीटस्टोन सेतु · विभवमापी · शून्य विक्षेप

Topics

• In a Wheatstone bridge the galvanometer reads zero when R₁/R₂ = R₃/R₄: the bridge is balanced.
• A metre bridge is a Wheatstone bridge whose two lower arms are a uniform wire 1 m long: resistance ∝ length.
• The jockey is moved along the wire until the galvanometer shows no deflection: this is the null point.
• With the null point at l cm from the left, the unknown resistance is X = R(100 − l)/l.
• A potentiometer wire carries a steady current, so the potential drop along it is proportional to length.
• Comparing EMFs: balancing lengths l₁ and l₂ for two cells give E₁/E₂ = l₁/l₂.
• A resistor R across the cell cuts the balancing length from l₁ to l₂; its internal resistance r = R(l₁ − l₂)/l₂.
• A potentiometer measures EMF exactly because at balance it draws no current from the cell under test.

About this model

A GLB file of about 365 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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