1.Units, Dimensions and Measurement
medium

Answer the following :

$(a)$ You are given a thread and a metre scale. How will you estimate the diameter of the thread ?

$(b)$ A screw gauge has a pitch of $1.0\; mm$ and $200$ divisions on the circular scale. Do you think it is possible to increase the accuracy of the screw gauge arbitrarily by increasing the number of divisions on the circular scale ?

$(c)$ The mean diameter of a thin brass rod is to be measured by vernier callipers. Why is a set of $100$ measurements of the diameter expected to yield a more reliable estimate than a set of $5$ measurements only ?

Option A
Option B
Option C
Option D

Solution

Wrap the thread on a uniform smooth rod in such a way that the coils thus formed are very close to each other. Measure the length of the thread using a metre scale. The diameter of the thread is given by the relation,

Diameter $=\frac{\text { Length of thread }}{\text { Number of turns }}$

It is not possible to increase the accuracy of a screw gauge by increasing the number of divisions of the circular scale. Increasing the number divisions of the circular scale will increase its accuracy to a certain extent only.

A set of $100$ measurements is more reliable than a set of $5$ measurements because random errors involved in the former are very less as compared to the latter.

Standard 11
Physics

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