Question

You are given a wire and a metre scale. How will you estimate the
diameter of the wire?

Answer 1

Measuring of diameter of wire using a metre scale isn't a good option . You may measure the diameter of wire using a metre scale but I bet you that the readings won't be accurate because of the least count error. Though no measurements are exact but the measurements taken by the metre scale will have 
a very large error. So , instead of a metre scale use either screw gauge or micrometer gauge .

Answer 2

Answer:

(a) 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 = Length of rod/Number of turns

(b) 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 of divisions of the circular scale will increase its accuracy to a certain extent only.

(c) 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.