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in Physics by (44.7k points)

The pitch of screw gauge is 1 mm and there are 100 divisions on the circular scale. What measuring the diameter of a wire, the linear scale reads, 1 mm and 47th division on the circular scale coincides with the reference line. The length of the wire is 5.6 cm. What will be the curved surface area (in cm2) of the wire in appropriate number of significant figures. 

(A) 2.6 cm2 

(B) 2.5848 cm

(C) 2.585 cm2 

(D) 2.5 cm2

1 Answer

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by (69.7k points)
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Best answer

The correct option is (A) 2.6 cm2.

Explanation:

Least count = {(1 mm) / (100)} = 0.01 mm 

Diameter of wire = 1 mm + (47 × 0.01 mm) 

∴ d = 1.47 mm 

curved surface area = 2πrℓ 

= 2π(d / 2)ℓ 

= πdℓ 

= π × 1.47 × 10–1 × 5.6 

= 2.5848 cm

= 2.6 cm2 (in two significant digits).

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