Page 23 - Physics - XI

EXPERIMENT - 3

Aim

To determine volume of an irregular lamina using screw gauge.

Apparatus and Materials Required

Irregular lamina whose volume is to be measured, a screw gauge, a millimetre graph paper, a metre scale,
and a pencil with a pointed end

Principle/Theory

An irregular lamina has no regular geometrical shape and whose thickness is very small as compared to its
length and breadth.
Volume of an irregular lamina = area of lamina × mean thickness
The mean thickness of an irregular lamina can be measured with the help of a screw gauge.

The area of an irregular lamina can be measured with the help of a graph paper. As irregular lamina is
irregular in shape, so its area cannot be calculated by the simple formula.

Procedure

(i) Determination of area of an irregular lamina
1. Place the given irregular lamina fl at on the millimetre graph paper.
2. Draw the outline of the surface of the given lamina on the millimetre graph paper with the help of a
pencil.

3. Now, remove the lamina from the graph paper.
4. Count the number of full squares falling completely inside the outline and record their number on the
notebook.

5. Now, count the squares which are partly inside and partly outside the marked boundary. Count the
squares which are equal to or more than half inside the marked boundary as full squares and do not
count those squares which are less than half inside the boundary.

Fig. 3.1: Measuring area of an irregular lamina

6. The area of an irregular lamina will be equal to the number of full millimetre squares as counted in step
4 plus number of squares counted in step 5.

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