The instrument that converts mechanical energy into electrical energy is:
A. Galvanometer
B. Transformer
C. Generator
D. Electric motor
Answer: Option C
Solution (By JKExamLibrary)
Generator converts mechanical energy (rotation) to electrical energy via electromagnetic induction. Motor does the reverse (electrical to mechanical). Transformer changes AC voltage levels; galvanometer detects small currents. Memory aid: 'Generator: motion ⇒ electricity; Motor: electricity ⇒ motion'. This principle-based question tests understanding of energy conversion devices, crucial for electromagnetism in competitive exams. Always link device function to underlying physics law: generator (Faraday's law), motor (Lorentz force).
Explanation:
Astigmatism: cornea curvature not spherical, different focal lengths in different planes. Corrected by cylindrical lens which has different powers in perpendicular axes. Not simple spherical lens.
According to Kepler's Third Law of Planetary Motion, the square of the time period of revolution of a planet around the Sun is directly proportional to:
A.The mass of the planet
B.The cube of the mass of the Sun
C.The square of the semi-major axis of its elliptical orbit
D.The cube of the semi-major axis of its elliptical orbit
Explanation:
Kepler's Third Law (Law of Periods) states that the square of the time period (T^2) of any planet is proportional to the cube of the semi-major axis (r^3) of its orbit. Mathematically, T^2 is proportional to r^3. This law helps in calculating orbital periods or distances of planets and satellites.
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