Q67 / 75 · JEE Main 2026 (23 January Shift 1) · Physics

In a screw gauge, the zero of the circular scale lies 3 divisions above the horizontal pitch line when their metallic studs are brought in contact. Using this instrument thickness of a sheet is measured. If pitch scale reading is 1 mm and the circular scale reading is 51 then the correct thickness of the sheet is $\_\_\_\_$ mm.
[Assume least count is 0.01 mm ]

  • A
    $1.50$
  • B
    $1.48$
  • Correct answer
    C
    $1.54$
  • D
    $1.51$

Solution

For a screw gauge, the measurement formula is: Reading = Pitch scale + (Circular scale × Least count) - Zero error
The zero of circular scale lies 3 divisions above the pitch line, indicating negative zero error:
Zero error = -3 × 0.01 = -0.03 mm
Reading = 1 + (51 × 0.01) - (-0.03) = 1 + 0.51 + 0.03 = 1.54 mm

Hence, the correct answer is option: 'C'.

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