The variation of potential difference V with length ℓ for two potentiometers P and Q is shown. Which one would you prefer for comparing the EMFs of two primary cells?
Answer: Potentiometer Q is preferred, because it has the smaller potential gradient k=V/ℓ.
Solution
Sensitivity of a potentiometer is higher when its potential gradient k=V/ℓ is smaller — a smaller k gives a longer balancing length for a given EMF and hence finer measurement. The graph for Q has the smaller slope (V/ℓ), so Q is preferred.
CBSE Class 12 Board · 2006 · All India · Subjective
