Potentiometer Length and Accuracy – Rankers Physics
Topic: Current Electricity
Subtopic: Measuring Devices ( Galvanometer, Voltmeter and Ammeter & Meter Bridge )

Potentiometer Length and Accuracy

Assertion (A): A potentiometer of longer length is used for accurate measurement.
Reason (R): The potential gradient for a potentiometer of longer length with a given source of e.m.f. becomes small.
 
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) Both (A) and (R) are false

Solution:

A longer potentiometer wire, for a given driver cell, results in a smaller potential gradient \( k = V/L \). A smaller potential gradient means that even a small change in potential corresponds to a significant change in balancing length, increasing the sensitivity and accuracy of the measurement. Thus, both (A) and (R) are true, and (R) correctly explains (A).

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