Physics Practicals - For Class IX (Science Group) - PRACTICAL 01: Determine the Diameter of a small sphere using a Micrometer Screw Gauge and calculate its volume.

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PRACTICAL 01:

Determine the Diameter of a small sphere using a Micrometer Screw Gauge and calculate its volume.

APPARATUS:

• Screw gauge
• Small sphere

THEORY:
Micrometer screw gauge consists of a U - shaped steel frame of a fixed stud and a movable stud, which can move in a hollow cylinder called drum or thimble. It has two scales one is called main scale and other is called circular scale.

LEAST COUNT:
Smallest distance that can be measured by it called least count.

PITCH:
It is the perpendicular distance between the two adjacent threads.

ZERO ERROR:
When two studs of screw gauge are in contact and zero of main scale does not coincide with the zero of the circular scale then screw gauge is said to have zero error.

FORMULA: (1 MARK)
Volume of sphere = ⁴/₃ πr³

METHOD: (2 MARKS)

• Find pitch of screw gauge by giving one rotation to circular scale.
• Calculate least count of screw gauge.
• Remove zero error if present.
• Place the sphere between studs and screw up till thc sphere heId gently. Note main scale reading and circular scale reading at line of reference.
• Multiply circular scale reading and least count to get fractional part.
• Add main scale reading and fractional part to get total diameter.
• Take three readings each time fixing the sphere from a different side.

OBSERVATIONS: (2 MARKS)
Pitch of screw gauge = 1 mm = I/10 cm = 0.1 cm
Least count = Pitch of the screw gauge / No. of circular scale divisions
L.C. = 0.1 / 100 = 0.001 cm

DIAMETER OF SPHERE:

OBS	MAIN SCALE READING (M.S.R) cm	CIRCULAR SCALE READING (C.S.R) div	FRACTIONAL PART F.P. = C.S.R x L.C cm	TOTAL DIAMETER D = M.S.R + F.P cm
	1.2 cm	70 div	70 x 0.001 = 0.07 cm	1.2 + 0.07 = 1.27 cm
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2
3

CALCULATIONS: (1+4 MARKS)

RESULT:
Mean Diameter of sphere = _____ cm and
Volume of sphere = _____ cm³

FIGURE: (2 MARKS)

PRECAUTIONS:

• If there is zero error then it must be removed.
• Reading must be taken at different points of the spheres.

Special Thanks to Sir Sajjad Akber Chandio