question_answer 8)

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 calipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only ?  

Answer:

(a) The thread is wound on the metre scale so that its turns are as close as possible. Thickness  of the thread coil is measured and the number of turns  of the thread coil is counted. Thickness of thread . (b) Least count of a screw gauge Theoretically, it appears that the least count can be decreased by increasing the number of divisions on the circular scale. Practically, it may not be possible to take the reading precisely due to low resolution of human eye. (c) Larger the number of readings, closer is the arithmetic mean to the true value and hence smaller the random error. Hence result with a set of 100 measurements is more reliable than that with a set of 5 measurements.