Answer the following :
You are given a thread and a metre scale. How will you estimate the diameter of the thread ?

Explanation

The diameter of a thread is so small that it cannot be measured using a metre scale. We wind a number of turns of the thread on the metre scale. So that the turns are closely touching one another. Measure the length (l) of the windings on the scale which contains n number of turns.
`therefore` Diameter of thread `=1/n`