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JEE Advanced 2026Paper 2
Exam
JEE Advanced
Year
2026
Paper
Paper 2
Subject
Physics
Chapter
Experimental Physics

JEE Advanced 2026 · Paper 2 · Physics · Experimental Physics

Two thin wires, Wire-1 of diameter 0.650 mm and Wire-2 of unknown...

Two thin wires, Wire-1 of diameter 0.6500.650 mm and Wire-2 of unknown diameter dd are given. To obtain the value of dd, the diameters of the two wires are measured with a screw gauge. The screw gauge has a pitch of 0.50.5 mm and there are 100100 divisions on the circular scale (CS). The smallest division on the linear scale (LS) is 0.50.5 mm. The table shows the readings of LS and CS for the measurements. The value of dd (in μ\mum) is:
Readings
LS (mm)CS
Wire-10.50.54242
Wire-21.51.59595

Correct answer

0

Step-by-step solution

The least count (LC) of the screw gauge is given by:

LC=PitchNumber of divisions on CS=0.5100=0.005 mm\text{LC} = \dfrac{\text{Pitch}}{\text{Number of divisions on CS}} = \dfrac{0.5}{100} = 0.005 \text{ mm}

For Wire-1, the measured reading is:

Reading1=LS+CS×LC\text{Reading}_1 = \text{LS} + \text{CS} \times \text{LC}

Reading1=0.5+42×0.005=0.5+0.210=0.710 mm\text{Reading}_1 = 0.5 + 42 \times 0.005 = 0.5 + 0.210 = 0.710 \text{ mm}

The actual diameter of Wire-1 is 0.650 mm0.650 \text{ mm}. The zero error of the screw gauge is:

Zero Error=Measured Reading−Actual Value=0.710−0.650=+0.060 mm\text{Zero Error} = \text{Measured Reading} - \text{Actual Value} = 0.710 - 0.650 = +0.060 \text{ mm}

For Wire-2, the measured reading is:

Reading2=LS+CS×LC\text{Reading}_2 = \text{LS} + \text{CS} \times \text{LC}

Reading2=1.5+95×0.005=1.5+0.475=1.975 mm\text{Reading}_2 = 1.5 + 95 \times 0.005 = 1.5 + 0.475 = 1.975 \text{ mm}

The actual diameter dd of Wire-2 is obtained by subtracting the zero error from its measured reading:

d=Reading2−Zero Error=1.975−0.060=1.915 mmd = \text{Reading}_2 - \text{Zero Error} = 1.975 - 0.060 = 1.915 \text{ mm}

Converting the diameter into micrometers (μ\mum):

d=1.915×1000 μm=1915 μmd = 1.915 \times 1000 \text{ } \mu\text{m} = 1915 \text{ } \mu\text{m}

Answer: 19151915
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