EXPERIMENT NO 01: To measure the diameter of a pen by using screw gauge and area of its

section. THEORY: Micrometer screw-gauge is another instrument used for measuring accurately the diameter of a pen It consists of a U-shaped frame fitted with a screwed spindle which is attached to a thimble. The screw has a known pitch such as 1 mm. Pitch of the screw is the distance moved by the spindle per revolution. Hence in this case, for one revolution of the screw the spindle moves forward or backward 1 mm. This movement of the spindle is shown on an engraved linear millimeter scale on the sleeve. On the thimble there is a circular scale which is divided into 50 or 100 equal parts. When the anvil and spindle end are brought in contact, the edge of the circular scale should be at the zero of the sleeve (linear scale) and the zero of the circular scale should be opposite to the datum line of the sleeve. If the zero is not coinciding with the datum line, there will be a positive or negative zero error. While taking a reading, the thimble is turned until the wire is held firmly between the anvil and the spindle. APPARATUS: Screw gauge and a pen whose diameter and area has to be found. PROCEDURE:

1) First we closed both the jaws to find whether there is zero error or not.In this case there was no zero error.

2) Then we placed the given wire in between both the jaws of screw gauge. 3) After that we found the main scale reading and also the conciding circular scale

division. 4) At the end we calculated the diameter of the given wire by putting the values in

the formula. SL Linear scale

reading x mm Circular scale division n

Least count mm

Value of circular scale reading Y=n×L.C

Diameter D=X+Y mm

Mean diameter mm

1 7.5 30 2 7.5 15 0.01 3 7.5 14 4 7.5 17 5 7.5 16

OBSRVATIONS AND CALCULATIONS:

1. Determination of Least Count of the Screw Gauge 1L.S.D. = 1mm Number of full rotations given to screw = 4 Distance moved by the screw = 4 mm

Hence, pitch=4mm4 =1mm Number of divisions on circular scale = 100 Hence, least count = 1mm100 = 0.01 mm = 0.001 cm. 2. Zero Error. zero error (e) = mm

zero correction (c) = …….mm. Diameter of pen = Radius of the pen= Area of the pen= Result: Diameter of pen = Area of the pen=

PRECAUTIONS 1. To avoid undue pressure; the screw should always be rotated by ratchet R and not by cap K. 2.The screw should move freely without friction. 3.The zero correction, with proper sign should be noted very carefully and added algebraically. 4.For same set of observations, the screw should be moved in the same direction to avoid back-lash error of the screw. 5.At each place, the diameter of the wire should be measured in two perpendicular directions and then the mean of the two be taken. 6.Readings should be taken at least for five different places equally spaced along the whole length of the wire.

7.Error due to parallax should be avoided. CONCLUSION: From this experiment we found that what is screw gauge and how to use it to find the diameter of a object.