Question

Which of the following statements about the Vernier callipers are true?
(A) It can be used to measure internal diameters.
(B) It can be used to measure external diameters.
(C) It is accurate up to $0.1cm$
(D) A zero error may be present.

Answer 1

Hint : Vernier callipers have both internal jaws and external jaws. Every scientific measurement equipment can have zero error.

Complete step by step answer
A Vernier calliper is a scientific measuring equipment used in measuring linear length (as opposed to measuring equipment like tape rule which can be used to measure curved length like circumference). The equipment has parts designed for different purposes, to ensure that it measures accurately for different circumstances. Some of these parts are
The main scale – the main scale of a Vernier calliper inscribed on a thick non flexible material to measure linear lengths. It is inscribed similarly to a ruler and has a resolution of 1 mm.
The Vernier scale – this is the scale exclusive to the Vernier calliper, usually designed to be at the end of the jaws of the calliper so it can be movable. It has a resolution of about 0.1 – 0.01 mm
The external jaws, these are the parts of the Vernier calliper designed to allow measurement of external diameters of an object. The jaws are adjustable and connected to the Vernier scale so it can move according to the diameter.
The internal jaws - these are the parts of Vernier calliper designed to allow measurement of internal diameters of an object. The jaws are also adjustable and connected to the Vernier scale so it can move according to the size of the object.
In general, the Vernier calliper has accuracy up to 0.01 mm, and also has zero error.
Hence, the correct options are A, B, D.

Note
For clarity, the zero error of a calliper originates from when the zero mark of the Vernier scale does not coincide with the zero mark of the main scale. The whole number of a Vernier calliper reading is the point where the zero mark of the Vernier scale points on the main scale. Hence, if the at no readings, the zero mark of Vernier scale does not coincide with the zero mark main scale, this means the reading of the Vernier calliper in general must be offset by the zero mark error.