To Measure The Thickness Of The Given Sheet Using Screw Gauge - Practice Questions & MCQ

Aim-

To measure the thickness of the given sheet using a screw gauge

Apparatus
Screw gauge, Sheet, half-metre scale and magnifying lens.

Theory
1. If we place sheet between plane faces A and B, the edge of the cap lies ahead of Mb division of linear scale. Then, linear scale reading (L.S.R.) =N.
If nth division of circular scale lies over reference line.
Then, circular scale reading (C.S.R) = n x (L.C.)                                                         (Here, L.C. is least count of screw gauge)

Total reading (TR) = LS.R. + C.S.R. =N+n (L . C .)

Procedure -

1.    Note the number of divisions on the circular scale.

2.    Give five complete rotations to the screw.

3.    Note the linear distance moved by the screw.

4.    Find the pitch and L.C. of screw gauge.

5.    Find the zero error and zero correction by moving the screw only in one direction in such a way that studs A and B just touch each other.

6.    Now grip the given sheet in the gap A and B of the screw gauge.

7.    Turn the screw head till the ratchet arrangement gives a click.

8.    Note the readings of linear scale and circular scale and find the observed thickness using the relation, observation thickness = L.S.R. + C.S.R.

9.    Add the zero correction to the observed thickness to find the corrected diameter.

10.  Repeat steps 6 to 9 to find the thickness from four more different places.

Calculations -

C.S.R = circular scale reading

$
\begin{aligned}
\text { Total reading } & =\text { M.S.R }+ \text { C.S.R } \\
& =M S R+L C \times C S R
\end{aligned}
$
 

L.C = least count

C.S.R = Circular scale reading

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.