Potentiometer Principle

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Potentiometer measures EMF accurately because it draws:

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A potentiometer uses the **Null Point** method.
- At the balancing point, the potential from the secondary circuit exactly matches that from the potentiometer wire segment.
- Consequently, no current flows from the test cell ($I = 0$).
- Since $V = E - Ir$ and $I=0$, the potentiometer measures the **actual EMF ($E$)** rather than the terminal voltage ($V$). This makes it a primary measurement tool unlike a voltmeter which always draws some current.

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Potentiometer Principle

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