Units and Measurement
© examsnet.com
Question : 8
Total: 33
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?
(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?
Solution:
(a) The diameter of a thread is so small that it cannot be measuredusing a metre scale. We wind a number of turns of the thread on the metrescale so that the turns are closely touching one another. Measure thelength ( l ) n
∴ =
(c) A large number of observations (say, 100) will give more reliableresult than smaller number of observations (say, 5). This is because largerthe number of readings, closer is the arithmetic mean to the true valueand hence smaller the random error.
(b) As least count =
∴ theoretically speaking, least count decreases on increasing thenumber of divisions on the circular scale. Hence, accuracy would increase.Practically, it may not be possible to take the reading precisely due to lowresolution of human eye.(c) A large number of observations (say, 100) will give more reliableresult than smaller number of observations (say, 5). This is because largerthe number of readings, closer is the arithmetic mean to the true valueand hence smaller the random error.
© examsnet.com
Go to Question: