Experimental Skills | Physics JEE previous year questions with Solutions

Q 11 :

For the determination of refractive index of glass slab, a travelling microscope is used whose main scale contains 300 equal divisions equals to 15 cm. The vernier scale attached to the microscope has 25 divisions equals to 24 divisions of main scale. The least count (LC) of the travelling microscope is (in cm): [2025]

0.001
0.002
0.0005
0.0025

1

2

3

4

(2)

$300 msd = 15 cm$

$1 msd = \frac{15}{300} = 0.05 cm$

$25 vsd = 24 msd$

$1 vsd = \frac{24}{25} msd$

$LC = 1 msd - 1 vsd$

$LC = 1 msd - \frac{24}{25} msd = \frac{1}{25} msd$

$LC = \frac{1}{25} \times 0.05 = 0.002 cm$

Q 12 :

In an experiment with Vernier callipers of least count 0.1 mm, when two jaws are joined together the zero of Vernier scale lies right to the zero of the main scale and 6th division of Vernier scale coincides with the main scale division. While measuring the diameter of a spherical bob, the zero of vernier scale lies in between 3.2 cm and 3.3 cm marks, and 4th division of vernier scale coincides with the main scale division. The diameter of bob is measured as [2023]

3.18 cm
3.25 cm
3.26 cm
3.22 cm

1

2

3

4

(1)

$L C = 0 . 1 mm$

$Zero Error = 6 \times L C = 0.6 mm$

$Reading = MSR + VSR \times L C - Zero Error$

$= [32 mm + (0.1) 4 mm] - 0.6 mm$

$= 31.8 mm = 3.18 cm$

Q 13 :

In an experiment, a set of reading are obtained as follows – 1.24 mm, 1.25 mm, 1.23 mm, 1.21 mm. The expected least count of the instrument used in recording these readings is ______ mm. [2026]

0.05
0.01
0.001
0.001

1

2

3

4

(2)

Q 14 :

In a vernier callipers, 50 vernier scale divisions are equal to 48 main scale divisions. If one main scale division = 0.05 mm, then the least count of the vernier callipers is ____ mm. [2026]

0.05
0.02
0.002
0.005

1

2

3

4

(3)

Q 15 :

When both jaws of vernier callipers touch each other, the zero mark of the vernier scale is right to the zero mark of the main scale. The 4th mark on the vernier scale coincides with a certain mark on the main scale.

While measuring the length of a cylinder, the observer notes 15 divisions on the main scale and the 5th division of the vernier scale coincides with a main scale division.

Measured length of the cylinder is ______ mm.
(Least count of Vernier calliper = 0.1 mm) [2026]

15.4
15.1
15.9
15.5

1

2

3

4

(2)

Topic Question Set

Q 13 :

In an experiment, a set of reading are obtained as follows – 1.24 mm, 1.25 mm, 1.23 mm, 1.21 mm. The expected least count of the instrument used in recording these readings is ______ mm. [2026]

Q 14 :

In a vernier callipers, 50 vernier scale divisions are equal to 48 main scale divisions. If one main scale division = 0.05 mm, then the least count of the vernier callipers is ____ mm. [2026]

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