Experiment 1 Diameter of Bob using Vernier Calliper 11th Class

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AIM • Use of Vernier Callipers to • (i) measure diameter of a small spherical/cylindrical body, • (ii) measure the dimensions of a given regular body of known mass • and hence to determine its density; and • (iii) measure the internal diameter and depth of a given cylindrical object • like beaker/glass/calorimeter and hence to calculate its volume. • APPARATUS AND MATERIAL REQUIRED • Vernier Callipers, Spherical body, such as a pendulum bob or a glass • marble, rectangular block of known mass and cylindrical object like • a beaker/glass/calorimeter • DESCRIPTION OF THE MEASURING DEVICE • 1. A Vernier Calliper has two scales–one main scale and a Vernier • scale, which slides along the main scale. The main scale and Vernier • scale are divided into small divisions though of different • magnitudes. • The main scale is graduated in cm and mm. It has two fixed jaws, A • and C, projected at right angles to the scale. The sliding Vernier scale • has jaws (B, D) projecting at right angles to it and also the main scale • and a metallic strip (N). The zero of • main scale and Vernier scale coincide • when the jaws are made to touch each • other. The jaws and metallic strip are • designed to measure the distance/ • diameter of objects. Knob P is used to • slide the vernier scale on the main • scale. Screw S is used to fix the vernier • scale at a desired position. • 2. The least count of a common scale • is 1mm. It is difficult to further • subdivide it to improve the least • count of the scale. A vernier scale • enables this to be achieved. • PRINCIPLE • The difference in the magnitude of one main scale division (M.S.D.) • and one vernier scale division (V.S.D.) is called the least count of the • instrument, as it is the smallest distance that can be measured using • the instrument. • n V.S.D. = (n – 1) M.S.D. • Formulas Used • (a) Least count of vernier callipers • the magnitude of the smallest division on the main scale • the total number of small divisions on the vernier scale = • (b) Density of a rectangular body = • mass m m • volume V l.b.h = = where m is • its mass, l its length, b its breadth and h the height. • (c) The volume of a cylindrical (hollow) object V = πr2h' = π ′2 D . h' • 4 • where h' is its internal depth, D' is its internal diameter and r is • its internal radius. • PROCEDURE • (a) Measuring the diameter of a small spherical or cylindrical • body. • 1. Keep the jaws of Vernier Callipers closed. Observe the zero mark of • the main scale. It must perfectly coincide with that of the vernier • scale. If this is not so, account for the zero error for all observations to • be made while using the instrument as explained on pages 26-27. • 2. Look for the division on the vernier scale that coincides with a • division of main scale. Use a magnifying glass, if available and • note the number of division on the Vernier scale that coincides • with the one on the main scale. Position your eye directly over the • division mark so as to avoid any parallax error. • 3. Gently loosen the screw to release the movable jaw. Slide it enough • to hold the sphere/cylindrical body gently (without any undue • pressure) in between the lower jaws AB. The jaws should be perfectly • perpendicular to the diameter of the body. Now, gently tighten the • screw so as to clamp the instrument in this position to the body. • 4. Carefully note the position of the zero mark of the vernier scale • against the main scale. Usually, it will not perfectly coincide with • PRINCIPLE • The difference in the magnitude of one main scale division (M.S.D.) • and one vernier scale division (V.S.D.) is called the least count of the • instrument, as it is the smallest distance that can be measured using • the instrument. • n V.S.D. = (n – 1) M.S.D. • Formulas Used • (a) Least count of vernier callipers • the magnitude of the smallest division on the main scale • the total number of small divisions on the vernier scale = • (b) Density of a rectangular body = • mass m m • volume V l.b.h = = where m is • its mass, l its length, b its breadth and h the height. • (c) The volume of a cylindrical (hollow) object V = πr2h' = π ′2 D . h' • 4 • where h' is its internal depth, D' is its internal diameter and r is • its internal radius. • PROCEDURE • (a) Measuring the diameter of a small spherical or cylindrical • body. • 1. Keep the jaws of Vernier Callipers closed. Observe the zero mark of • the main scale. It must perfectly coincide with that of the vernier • scale. If this is not so, account for the zero error for all observations to • be made while using the instrument as explained on pages 26-27. • 2. Look for the division on the vernier scale that coincides with a • division of main scale. Use a magnifying glass, if available and • note the number of division on the Vernier scale that coincides • with the one on the main scale. Position your eye directly over the • division mark so as to avoid any parallax error. • #RathourClasses • Join my telegram channel to get latest updates • https://t.me/RathourClasses

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