Vernier caliper is a measuring device that has two scales: the main scale and vernier scale such that the vernier scale slides over the main scale. The main scale is divided into small divisions in cm and mm and has two fixed jaws A and C. B and D are the jaws of the vernier scale. When the jaws of scales are made to touch, the zero of both the scales coincide. Below is an experiment to determine the internal diameter and depth of a beaker and hence to find the volume.
Aim
To measure internal diameter and depth of a beaker/calorimeter using vernier calipers and hence find its volume.
Materials Required
 Vernier calipers
 A cylindrical object like a beaker
 Magnifying glass
Theory
What is least count?
The least count is defined as the smallest change in the measured quantity which can be resolved on an instrument’s scale.
How to calculate least count?
The least count of vernier caliper = Least count of vernier caliper = \(\frac{frac\,magnitude\,of\, the\, smallest\, division\, on \,the \,main \,scale}{total\, number\, of\, small \,divisions\, on \,the \,vernier\, scale}\)
The formula used to calculate the volume of beaker/calorimeter = internal area of crosssection × depth
\(V=(\frac{D}{2})^{2}.d\) 
Where,
 D is the internal diameter of the beaker/calorimeter
 d is the depth of the beaker/calorimeter
Diagram
Procedure
 Determine and record the least count of the vernier caliper which is also known as the vernier constant.
 To find the zero error, bring the movable jaw BD in contact with the fixed jaw AC. Repeat and record this three times. If there is no zero error, then record zero error as nil.
 Now put the jaws C and D inside the beaker and open till they make contact with the inner wall of the beaker without any pressure. Tighten the screw without putting too much of pressure.
 On the main scale, record the zero mark of the vernier scale. Just before the zero mark of the vernier scale, record the main scale reading which is known as main scale reading (M.S.R).
 Let n be the number of the vernier scale division which coincides with the main scale division.
 Rotate the vernier caliper 90° and repeat the steps 4 and 5 for measuring the internal diameter in perpendicular direction.
 To measure the depth, find the total reading and zero correction.
 The edge of the main scale of vernier caliper should be placed on the peripheral edge. Care should be taken to make the strip go freely inside the beaker along with its depth.
 Once the moving jaw of the vernier caliper touches the bottom of the beaker perpendicularly, the screw of the vernier caliper should be tightened.
 For four different positions along the circumference of the beaker, repeat steps 4 and 5.
 Find the total reading and also zero correction.
 For internal diameter, take two different mean values and for depth, take four different values.
 Calculate the volume using the proper formula and record the same in the result with units.
Observations

 Determination of the least count of vernier caliper1 M.S.D = 1 mm 10 V.S.D = 9 M.S.D
∴ 1 V.S.D = 9/10 M.S.D = 0.9 mm
The least count of vernier caliper (V.C) = 1 M.S.D – 1 V.S.D = (10.9) mm = 0.1 mm = 0.01 cm
 Zero error = (i)…. cm (ii)…. cm (iii)…..cmMean zero error (e) = …..cm
Mean zero correction © = (e) = …….cm
 Table for internal diameter (D)
Sl. no Main scale Vernier scale reading Total reading No.of vernier division coinciding (n) Value [n×(V.C)] Observed D_{0}=N+n×V.C Corrected D=D_{0}+c 1. D_{1}= 2. D_{2}= 3. D_{3}= 4. D_{4}=  Table for the depth (d)
 Determination of the least count of vernier caliper1 M.S.D = 1 mm 10 V.S.D = 9 M.S.D
Sl.no  Position  Main scale reading (N in cm)  Vernier scale reading  Total reading  
No.of vernier division coinciding (n)  Value [n×(V.C)]  Observed d_{0}=N+n × (V.C)  Corrected d=d_{0}+c  
1.  at A  d_{1}=  
2.  at B  d_{2}=  
3.  at C  d_{3}=  
4.  at D  d_{4}= 
Calculations
Mean corrected internal diameter,
\(D=\frac{D_{1}(a)+D_{1}(b)}{2}=…..\;cm\)Mean corrected depth,
\(d=\frac{d_{1}+d_{2}+d_{3}+d_{4}}{4}=…..\;cm\)Volume of the beaker,
\(V=\pi (\frac{D}{2})^{2}d=….\;cm^{3}\)Result
The volume of the beaker is …….cm^{3}.
Precautions
 Apply machine oil or grease to make the vernier scale slide smoothly over the main scale.
 To avoid the damage to threads, do not exert more pressure on the vernier screw.
 To avoid errors due to parallax, keep the eye directly over the division mark.
 The significant figures and units used in observations must be correct.
Sources Of Error
 Not accounting for the zero error in the instrument.
 Avoid gaps and undue pressure with respect to the placing of vernier calipers.
Viva Questions
Q1. What is the principle behind the vernier scale?
Ans: The principle behind the vernier scale is that the number of vernier scale divisions coinciding with the main scale division should be either one less or one more.
\(1 V.S.D=\frac{1 M.S.D}{no.\;of\;divisions\;on\;V.S}\) 
Q2. What is vernier constant?
Ans: Vernier constant is defined as the difference between the value of one main scale division and one vernier scale division on the vernier calipers.
Q3. What is least count of a measuring instrument?
Ans: The least count of a measuring instrument is defined as the least quantity that can be measured accurately.
Q4. What is the least count of vernier caliper?
Ans: The least count of the vernier caliper is 0.1 mm.
Q5. What is zero error?
Ans: Zeroerror is defined as how far away is the reading from zero for an instrument. It can be either positive or negative.
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