Verniers Calipers | Physics Practical XI


APPARATUS REQUIRED(i) Vernier calipers  (ii) Given Tube

THEORY :  The vernier calipers is a device used for measuring lengths in fractions of a millimeter with greater accuracy as compared to that of ordinary scale . It consists of main scale (MS) and vernier scale (VS) . The vernier scale (VS) slide over the main scale while main scale (MS) is fixed.

The vernier constant (VC) of the smallest length that can be measured accurately . It is the difference between  the values of the smallest division of the main scale (MS) and that of the vernier scale (VS). i.e.

VC = MS – VS                        (I)

In general n division of the vernier scale (VS) coincide with n-1 divisions of the main scale (MS) , So –

(n-1) MS = n VS

or, MS – VS =  MS / n

∴ VC = value of smallest main scale Division (MSD) ÷ Total Vernier Scale Division (VSD)

Length = MS reading + VS reading * VC ± Instrumental Error



l = length of the tube

d1 =external diameter  of the tube

d2 =internal diameter of the tube

We have ,

external volume(V1) = π/4 (d1)2l

internal volume(V2) = π/4 (d2)2l

∴ Volume of the tube (V) = V1-V2

∴ V = πl/4*(d22-d12)



a) Determination of Vernier Constant (Least Count) of the Vernier Calipers :

Value of 1 division of main scale = 1mm (MS)

10 VSD = 9 MSD

∴ 1 VSD = 9/10 MSD = 0.9 MSD = 0.9mm(VS)

∴ Vernier Constant (VC) = MS – VS = 1mm – 0.9mm = 0.1mm = 0.01cm

b) Measurement of volume :

Measurement with vernier calliper

   Obs for No. of Obs Reading of the Total

(1) + (3)

   MS (1) VS (2)   VS*VC (3)
Length (l) 1   l=…….cm
Ext. Diameter (d2) 1   d= …
Int. Diameter(d1) 1  d1 =….cm

Volume of the tube (V)  πl/4*(d22-d12) = ……… cm3
RESULT The volume of the given tube is …… cm3.


a) Ensure that the zero error is worked out properly before actual measurement.

b) Donot aapply excess pressure on the bodyheld between jaws.

c) All measurement must be done without parallax error.

d) Record all the reading in same system preferably in C.G.S system .

Important Questions

Physics Grade XI viva Question Vernier calliper

1: What is vernier calipers?
Ans. It is simple instrument by which length of an object can be measured accurately up to one-tenth of a millimeter or one-hundredth of a centimeter.

2: What is the use of Vernier Scale?
Ans. To increase the accuracy of the main scale.

3: What is least count (L.C.)?
Ans. The minimum measurement that can be taken by an instrument.

4: What is the least count of?
(a) meter scale (b) Stop Watch (c) Vernier Calliper
Ans. The least count of:
(a) meter scale = 0.1 cm or 1 mm.
(b) stop watch = 0.01 sec or 1/100 sec. or according to stop watch.
(c) vernier scale = 0.01 cm or 0.1 mm

5: What are units of vernier scale?
Ans. Vernier has not units of its own.

6: What is the difference in the measurement of one smaller division on the main scale (M.S.) and that of vernier scale (V.S.)
Ans. (1 smallest Div. on M.S.) – (1 smallest Div. on V.S) = 0.1 – 0.09 = 0.01 cm = Least count.

7: How the L.C. of a vernier is determined?
Ans. By using the relation:
L.C. = (Smallest division on Main Scale ) / (Total number of divisions on Vernier Scale)

8: Will the accuracy of a vernier will increase or decrease if 20 divisions are made in the same length?
Ans. The accuracy will increase since the L.C. will decrease i.e. Accuracy α = 1 / Least count

9: Which one is smaller M.S. div. or V.S. div.?
Ans. V.S. division.

10: 1 division on V.S. = _____ cm.
Ans. 0.09 cm.
10 div. on V.S. = 0.9 cm
1 div. on V.S. = 0.9/10 cm = 0.09 cm

11: What are the functions of (a) Sliding strip (b) Upper jaws
Ans. (a) For measuring depth. (b) For measuring the inner diameter.

12: What is meant by zero error (Z.E.)?
Ans. The error which arises when zeros of M.S. and V.S. do not coincide upon joining the two jaws.

13: When Z.E. is positive?
Ans. The Z.E. is positive when the zero of V.S. is to the right of the zero of M.S.

14: How we find the corrected reading?
Ans. Corrected reading = Meaning reading – ( + Z.E.)

.15: Do you know any use of vernier scale?
Ans. It is used in spectrometer, barometer, traveling microscope, etc.

16: What are significant figures?
Ans. Numbers 0, 1, 2, 3, ……. are called significant figures when they occur. The zero is not a significant figure if it is at the extreme left or extreme right of a number, e.g. 1.02 has three significant figures, but 1.20 has two significant figures.

17: What is meant by degree of accuracy?
Ans. It is the measurement estimated by the number of significant figures in the result.

18: Why is the vernier calipers so called?
Ans. A French mathematician named Pierre Vernier invented it and it is named after him.

19: How does temperature affect the length of a cylinder?
Ans. The length of a cylinder increases with the increase of temperature and decreases with the
decrease of temperature.

20: What is the unit of volume?
Ans. In MKS system, the unit of volume is m3. In CGS system, the unit of volume is cm3. In FPS
system, the unit of volume is ft3.



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