Which of the following is an application of electromagnetic induction? MCQ with Answer and Explanation
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Question #1
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A car travels from point A to B with speed 40 km/h and returns from B to A with speed 60 km/h. The average speed for the entire journey is:
Correct Answer: Option B
Explanation:
Average speed = Total distance / Total time. Let distance AB = d km. Time for AB = d/40 h, time for BA = d/60 h. Total distance = 2d km. Total time = d/40 + d/60 = d(3+2)/120 = 5d/120 = d/24 h. Average speed = 2d / (d/24) = 48 km/h. Note: Average speed is not arithmetic mean of speeds (which would be 50 km/h) because time intervals differ. This harmonic mean concept is crucial for motion problems. Exam tip: For equal distances, average speed = 2v₁v₂/(v₁+v₂). Frequently tested in competitive exams.
Average speed = Total distance / Total time. Let distance AB = d km. Time for AB = d/40 h, time for BA = d/60 h. Total distance = 2d km. Total time = d/40 + d/60 = d(3+2)/120 = 5d/120 = d/24 h. Average speed = 2d / (d/24) = 48 km/h. Note: Average speed is not arithmetic mean of speeds (which would be 50 km/h) because time intervals differ. This harmonic mean concept is crucial for motion problems. Exam tip: For equal distances, average speed = 2v₁v₂/(v₁+v₂). Frequently tested in competitive exams.
Question #2
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If the error in the measurement of the momentum of a particle is +100%, what will be the percentage error in the measurement of its kinetic energy?
Correct Answer: Option C
Explanation:
Kinetic Energy (K) is given by K = p^2 / 2m. If momentum (p) increases by 100%, the new momentum is p' = p + 1.0p = 2p. The new kinetic energy is K' = (2p)^2 / 2m = 4(p^2 / 2m) = 4K. The increase is 4K - K = 3K. Percentage increase = (3K/K) * 100 = 300%.
Kinetic Energy (K) is given by K = p^2 / 2m. If momentum (p) increases by 100%, the new momentum is p' = p + 1.0p = 2p. The new kinetic energy is K' = (2p)^2 / 2m = 4(p^2 / 2m) = 4K. The increase is 4K - K = 3K. Percentage increase = (3K/K) * 100 = 300%.
Question #3
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The device which converts mechanical energy into electrical energy is
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