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Question: Answered & Verified by Expert
The null point of a potentiometer with a cell of emf $\varepsilon$ is obtained at a distance $l$ on the wire, then
PhysicsCurrent ElectricityAP EAMCETAP EAMCET 2021 (25 Aug Shift 2)
Options:
  • A $\varepsilon \propto l$
  • B $\varepsilon \propto l^2$
  • C $\varepsilon \propto \frac{1}{l}$
  • D $\varepsilon \propto \frac{1}{l^2}$
Solution:
2234 Upvotes Verified Answer
The correct answer is: $\varepsilon \propto l$
As we know, electric field, $E=-\frac{d V}{d r}$
Hence, emf $\varepsilon$ is also directly proportional to $l$ i.e., $\varepsilon \propto l$.

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