JEE Mains · Physics · STD 11 - 1. units,dimensions and measurement
A screw gauge of pitch \(0.5\,mm\) is used to measure the diameter of uniform wire of length \(6.8\,cm\), the main scale reading is \(1.5\,mm\) and circular scale reading is \(7\). The calculated curved surface area of wire to appropriate significant figures is \(......cm^2\) . [Screw gauge has \(50\) divisions on the circular scale]
- A \(6.8\)
- B \(3.4\)
- C \(3.9\)
- D \(2.4\)
Answer & Solution
Correct Answer
(B) \(3.4\)
Step-by-step Solution
Detailed explanation
\( L.C.=\frac{P}{N}=\frac{0.5\,mm}{50}=0.01\,mm\) Length of wire \(=6.8 cm\) Diameter of wire \(=1.5\,mm +7 \times L.C\) \(=1.5\, mm +7 \times .01=1.57\,mm\) Curved surface area \(=\pi Dl\) \(=3.14 \times 6.8 \times 1.57 \times 10^{-1} cm^{2}\) \(=3.352\,cm ^{2}=3.4\,cm ^{2}\)
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