Page 24 - Physics - XI

(ii) Determination of the mean thickness of an irregular lamina
The mean thickness of an irregular lamina body can measured with the help of a screw gauge in the

same way as explained in the previous experiment.

Observations and Calculations
Volume of an irregular lamina = area of lamina × mean thickness

Result

The volume of the given irregular lamina is ________ mm .
3

VIVA VOCE

Q1. What is the least count of a screw gauge?
Ans. It is the distance moved by the screw gauge when it is rotated through one circular scale division. It
is given as

Pitch
Least count =
Total no. of divisions on the circular scale
Q2. Mention the diff erent types of motion possessed by the screw.

Ans. It has two types of motion
(i) linear motion
(ii) circular motion

Q3. What is the pitch of a screw gauge?
Ans. The linear distance moved by the screw when one complete rotation is given to the circular scale is
called the pitch of a screw gauge. Pitch is also defi ned as the perpendicular distance between two
successive threads of the screw.

Q4. What is the utility of the ratchet arrangement?
Ans. It is used to avoid excess pressure when the object is held between A and B.

Q5. Of what metal is the screw at the screw gauge made of and why?
Ans. The screw is made of gun metal to avoid wear and tear after a prolonged use.

Q6. State the principle of a screw gauge.
Ans. When a screw fi tted in a nut is rotated, a linear motion of the screw is produced. The linear motion
is directly proportional to the number of rotations given to the screw.

Q7. What is a screw gauge?
Ans. It is an instrument based upon the principle of micrometer screw. It is used to measure the distance
accurately upto 0.001 cm or even less than that.

Q8. Why is a screw gauge called a 'micrometer screw'?
Ans. It is so called because it can measure distance correctly to the order of the micrometer (10 m).
–6

22