The value of universal gravitational constant G is
A. 6.67 × 10⁻¹¹ N m²/kg²
B. 6.67 × 10⁻¹¹ dyne cm²/g²
C. 9.8 m/s²
D. Both A and C
Answer: Option D
Solution (By JKSSB Mock Tests)
G = 6.67 × 10⁻¹¹ N m²/kg² in SI, and 6.67 × 10⁻⁸ dyne cm²/g² in CGS. Both are correct. Important constant, measured by Cavendish. g is acceleration due to gravity, different.
Explanation:
Vernier caliper is ideal for measuring internal diameters of narrow tubes due to its internal jaws designed for such measurements. Screw gauge measures external dimensions like wire diameter. Meter scale and measuring tape lack the precision (least count ~1 mm) needed for narrow tubes. Vernier calipers typically have least count 0.01 mm or 0.02 mm. Practical tip: Always use internal jaws for internal measurements, external jaws for outer dimensions. This application-based question tests knowledge of instrument selection in experimental physics, commonly featured in practical examination sections.
Explanation:
The thermal efficiency (η) of a reversible Carnot engine depends exclusively on the absolute temperatures of the hot source (T1) and the cold sink (T2). The formula is η = 1 - (T2/T1), or (T1 - T2) / T1. Temperatures must be in Kelvin. It shows no engine can be 100% efficient unless the sink is at absolute zero.
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