Least counts of various instruments are as follows:
Meter Scale – 0.1cm, Vernier Caliper -0.1mm, Screw Gauge - 0.001cm, Spherometer-0.01 mm.
Which of these instruments has the least accuracy?
Answers
Answer:
Introduction
Length is a fundamental physical quantity. The devices generally used in the laboratory for measuring the length of a body are metre scale, vernier callipers, screw gauge and spherometer. The value of the marked division on metre scale is 1 mm. It can be used for measuring length with an accuracy of 1 mm. So the least count of a metre scale is 1 mm.
When we have to measure length accurately up to l/10th or l/100th of a millimetre, the following instruments are used :
(а) Vernier Callipers
(b) Screw Gauge
(c) Spherometer
Metre
It is the distance between the two parallel lines marked on a platinum-iridium rod preserved at a constant temperature of 273.16 K and pressure 1 bar in the International Bureau of Weights and Measures at Severes, near Paris in France.
Since 1960, the standard metre is defined as the distance which contains 16, 50, 763.73 wavelengths of orange-red light of krypton-86 (8636Kr) source kept at the temperature of triple point of nitrogen (which is 63.18 K at pressure 0.125 x 105 N m-2).