Verified Solution • 2025–26 Session moderate

QJEEM22Ph4403: JEE Main 2022 Physics - Class 11 JEEM22Ph4403 Solution: A screw gauge of pitch is used to measure the diameter of…

A screw gauge of pitch 0.5 mm0.5 \mathrm{~mm} is used to measure the diameter of uniform wire of length 6.8 cm6.8 \mathrm{~cm} , the main scale reading is 1.5 mm1.5 \mathrm{~mm} and circular scale reading is 7 . The calculated curved surface area of wire to appropriate significant figures is :

[Screw gauge has 50 divisions on its circular scale]

Multiple Choice Options

  • A 6.8 cm2
  • B 3.4 cm2
  • C 3.9 cm2
  • D 2.4 cm2

Step-by-Step Verified Solution

Least count =0.550= {{0.5} \over {50}} mm = 0.01 mm

∴\therefore Diameter, d = 1.5 mm + 7 ×\times 0.01

= 1.57 mm

∴\therefore Surface area =(2πr)×l= (2\pi r) \times l

=πdl= \pi dl

=3.142×1.5710×6.8= 3.142 \times {{1.57} \over {10}} \times 6.8 cm2

= 3.354 cm2 = 3.4 cm2

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