The material of a permanent magnet should have MCQ with Answer and Explanation
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Question #1
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A stone is thrown vertically upward with velocity 49 m/s. The time after which it returns to thrower is (g=9.8)
Question #2
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A ray of light passes from air to glass. Which quantity remains unchanged?
Correct Answer: Option D
Explanation:
When light crosses media, frequency remains constant as it's determined by the source. Speed and wavelength change proportionally: v = fλ, and v = c/n, so λ decreases in denser medium (glass). Amplitude may change due to reflection/transmission coefficients. Memory aid: 'Frequency is source-dependent; speed and wavelength are medium-dependent'. This fundamental wave property is frequently tested in refraction questions. Competitive exams often use this to assess understanding of wave behavior at interfaces. Always recall that color (frequency) doesn't change during refraction, though speed and wavelength do.
When light crosses media, frequency remains constant as it's determined by the source. Speed and wavelength change proportionally: v = fλ, and v = c/n, so λ decreases in denser medium (glass). Amplitude may change due to reflection/transmission coefficients. Memory aid: 'Frequency is source-dependent; speed and wavelength are medium-dependent'. This fundamental wave property is frequently tested in refraction questions. Competitive exams often use this to assess understanding of wave behavior at interfaces. Always recall that color (frequency) doesn't change during refraction, though speed and wavelength do.
Question #3
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Electric power P = VI. For 60W, 120V bulb, current is:
Correct Answer: Option A
Explanation:
I = P/V = 60/120 = 0.5 A. Direct power formula application. Memory tip: 'I = P/V for resistive loads; always use consistent units'. Basic electricity numerical frequently tested in competitive exams to verify formula application and unit handling.
I = P/V = 60/120 = 0.5 A. Direct power formula application. Memory tip: 'I = P/V for resistive loads; always use consistent units'. Basic electricity numerical frequently tested in competitive exams to verify formula application and unit handling.
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