JEE PYQ: Experimental Physics Question 1
Question 1 - 2021 (16 Mar 2021 Shift 1)
One main scale division of a vernier callipers is ‘a’ cm and $n^{\text{th}}$ division of the vernier scale coincide with $(n - 1)^{\text{th}}$ division of the main scale. The least count of the callipers in mm is:
(1) $\frac{10na}{(n-1)}$
(2) $\frac{10a}{(n-1)}$
(3) $\left(\frac{n-1}{10n}\right) a$
(4) $\frac{10a}{n}$
Show Answer
Answer: (4)
Solution
$(n-1)a = n(a’)$, so $a’ = \frac{(n-1)a}{n}$. L.C. $= 1\text{MSD} - 1\text{VSD} = (a - a’) \text{ cm} = a - \frac{(n-1)a}{n} = \frac{a}{n} \text{ cm} = \frac{10a}{n} \text{ mm}$.
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