Question

Name the instrument which can accurately measure the diameter of a pencil.
A. Screw gauge
B. Meter scale
C. Vernier calliper
D.All of the above

Answer 1

We find out the least counts of the given measuring instruments.
The accuracy of the measuring instrument depends on the least count of the measuring instruments.

Complete step by step answer:
The accuracy of the instrument has a direct relationship with the least count of the measuring instrument.
Therefore, if we find the least count of all of the given measuring instruments, we can find out which instrument is appropriate for measuring the diameter of the pencil.

Screw gauge
The least count of screw gauge is 0.001 mm. It is used for measuring the diameter of rods, wires, and other thin cables.

Meter scale
The least count of meter scale is 1 mm.

Vernier calliper
The least count of vernier callipers is 0.01 mm. It is used for measuring the width of rectangular blocks.
Therefore, the screw gauge having least count 0.001 mm will have the highest accuracy for measuring the diameter of the pencil since it has the smallest least count than other given measuring instruments.

So, the correct answer is “Option A”.

Note:
All of the given measuring instruments are able to measure the diameter of the pencil. But, the accuracy in the measurement of the diameter of the pencil will be achieved only with the micrometre screw gauge because of its smallest least count among the other measuring instruments. The only difference between screw gauge and vernier calliper is that the screw gauge is used to measure the outer diameter and vernier calliper is used to measure inner diameter as well as outer diameter.