callipers' jaws are used for measuring" low cylinder

dnouot
Ane thin metallic strip attached to the back side of the main scale is ue der or acalom
used for o
of a vessel.
13. Can we measure the thickness of a piece of paper by vernier callin. rnier callipers?
measurng
Ans. No.
laboratory Vernier Callipers?
Q.14. What is the least count of your
Ans. The least count is 0.01 cm.

vernier ?
Q.15. What is a n angular
used for measuring fraction of degree of
a .
Ans. An angular vernier is
an

angle. It is
sextants and spectrometers,
which m e a s u r e angular displacements. provide
EXPERIMENT 2
AIM: To measure diameter of a given wire using screw gauge.

APPARATUs
Screw gauge, wire, half-metre scale and magnifying lens.
THEORY
If with the wire between plane faces A and B, the edge of the cap lies ahead of Nth divigice
linear scale, then, linear scale reading (L.S.R.) = N.

If nth division of circular scale lies over reference line, then, circular scale
rea
(C.S.R)= nx (L.C.) (L.C. is least count of screw gauge)
Total reading (T.R.) = L.S.R. + C.S.R. = N+n x (L.C.).
IfD be the mean diameter and Ibe the mean length of the wire,
volume of the wire, VV=

DIAGRAM
Wire
AB N
H
E
E K

Fig. Screw
gauge measuring diameter of the wire.
Measurementof Length
PROCEDURE
41

Find the value of one linear scale

division (L.S.D.).
Dotermine the pitch
and the least count of the screw
Rring the plane face B in contact with gauge and record it
plane face A and find the zero
stepwise.
and record them. there is no
If error. Do it three times
zero error, then record zero
Move the face B away error as nil.
from face A. Place the wire
towards face A using the ratchet head R. lengthwise over face A and move the faceB
Stop when R turns (slips) without
Note the number of divisions of the moving the screw.
linear scale visible and
The reading (N) is called lHinear scale uncovered by the edge of the
reading (L.S.R.). cap
Note the number (n) of the division of
the circular scale
Repeat steps 5 and 6 after lying over reference line.
rotating the wire by 90° for
direction. measuring diameter in a perpendicular
8. Repeat steps 4, 5, 6 and 7 for five different
of the wire. Record the
positions separated equally throughout the length
observations in each set in a tabular form.
9. Find total reading and apply zero correction in
each case.
10. Take mean of different values of diameter.
11. Measure the length of the wire by stretching it
along a half-metre scale. Keeping one end of
wire at known mark, note the
a
position other end. Difference in position of the two ends
of
of the wire gives the length of the wire. Do
it three times and record them.

OBSERVATIONS

1. Determination of Least Count of the Screw Gauge

1 L.S.D. = 1 mm

Number of full rotations given to screw =4

Distance moved by the screw =4 mm

4 mm
Hence, pitchp- =. 1 mm
4

Number of divisions on circular scale = 100

1 mm
Hence, least count,= 100 = 0.01 mm = 0.001 cm.

2. Zero Error. (1u)... mm.

(i).. mm, (11) mm,

Mean zero error (e) = .... mmn

ean zero correction (¢) - e =..mm.=

2
Comrehenstue Practical Physir
3. Table for diameter (D)

Crcular Scale Reading

ysics
Total Readin
Linear Scale Value
Serial No. of
Readtng (N)
No. ofCircular

Scale division on In x(L.C)]

Observed

D-CorDrectel
Obeervations (mm) refevence Hne
D N+n
xL.C.
(mm) (mm)

(a) AB D,la
1

C6)D D,6)
(a)AB D,la
2

D, (b)=
(a) AB
3

D,6)
CALCULATIONS
Length of the wire, I = (i)... cm, i ) . . . m, (ii)... cm.
Mean diameter of the wire,
D= P,a)+D,(6)t. . + D,(a) + D, (6)
6
..... m m = ...... Cm

Mean length of the wire,

1 . Cm
3
Volume of the wire,

V=
.cm3
RESULT
The volume of
the given wire is ..
cm°.
PRECAUTIONS
1. To
avoid undue pressure; the
2. The screw screw should always be rotated ratchet R and
not bycap
should move by
freely without friction.
Measurement of Length
43
he zero correction, with proper sign should be noted very carefully and added algebraicaly.
Eor same set of observations, the screw should be moved in the same direction to avoid back

lash error of the screw

Ateach place, the diameter of the wire should be measured in two perpendicular directions
and then the mean of the two be taken.

Readings should be taken atleast for five different places equally spaced along the whole length
of the wire.

Error due to parallax should be avoided.

SOURCES OF ERROR

The screw may have friction.

The screw gauge may have back-lash error.

Circular scale divisions may not be of equal size.

4. The wire may not be uniform.

EXPERIMENT 2A
AIM: To measure thickness of a given sheet using screw gauge.

APPARATUS

Screw gauge, sheet (it must be rigid) and magnifying lens.

THEORY
Same as in Experiment 2.

PROCEDURE
to 6 in Experiment 2.
Steps 1 are same as

the surface of the sheet.

Repeat steps 4, 5, 6 for 5 different positions spread equally throughout
Record observation in tabular form.
in each case.
Find total reading and apply zero correction
Take mean of different values of thickness.

OBSERVATIONS
. Determination of least count of the screw gauge.

Same as in Experiment 2.

2. Zero Error.

Same as in Experiment 2.
44 kenstve Practical Phiysies
Table for the thickness (t)

Circular Scale Reading

Linear Scale
Serial Total Reading
No. Reading (N No. of Circular Value
Observed
(m) Scale division on In x (L.C.
ttCorrectal
t N+n
Observations reference Hne
L.C.
(n) (mm) (mm)
1.
mm
t
3.

CALCULATIONS
1. Find value of t for each observation and write the observed value t, in column(4)
Write corrected value oft in column (4b).
3. Find mean of values of t recorded in column (4b).

Mean thickness of the sheet, t = Gtt+t mm.

4

RESULT
The thickness of the given sheet is.. mm.

PRECAUTIONS
Same as in Experiment 2.

SOURCEs OF ERROR
Same as in
Experiment 2.

EXPERIMENT 3
AIM: To determine
volume of an
irregular lamina using screw gauge.
APPARATUUS
a pencil. crew gauge, an irregular lamina (it must be of netregraphpap

uniform thickness), a
cen
THEORY
Same as in
Experiment 2.