भौतिक विज्ञान (Physics) – Physics MCQ
भौतिक विज्ञान (Physics) – इन्जिनियरिङ प्रवेश
Physics · Engineering Entrance – Mathematics, Physics, Chemistry & English · १,३९८ प्रश्न
१,३९८ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान (Physics): प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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The dimensional formula of angular momentum is:
सही उत्तर: क) [M L² T⁻¹]
Angular momentum = mvr, so its dimensions are [M][L T⁻¹][L] = [M L² T⁻¹] (the same as Planck's constant).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two thin convex lenses, each of focal length 20 cm, are placed coaxially 10 cm apart. The equivalent focal length of the combination is:
सही उत्तर: घ) 13.3 cm
1/F = 1/f₁ + 1/f₂ − d/(f₁f₂) = 1/20 + 1/20 − 10/400 = 3/40, so F = 13.3 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A mass hung on a light spring stretches it by 2.5 cm in equilibrium. When pulled down and released, its period of oscillation is about (g = 10 m/s²):
सही उत्तर: ग) 0.31 s
k/m = g/x₀, so T = 2π√(x₀/g) = 2π√(0.025/10) = 2π × 0.05 ≈ 0.31 s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The fraction of the nuclei of a radioactive sample that decay during a time equal to one mean life is about:
सही उत्तर: ख) 63%
N = N₀e^{−t/τ}; after t = τ the fraction left is 1/e ≈ 0.37, so about 63% have decayed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 0.5 kg stone tied to a 1 m string moves in a vertical circle. At the highest point its speed is 4 m/s. The tension in the string there is (g = 10 m/s²):
सही उत्तर: क) 3 N
At the top T + mg = mv²/r: T = 0.5 × 16/1 − 0.5 × 10 = 8 − 5 = 3 N.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A ball is thrown at 20 m/s at 30° above the horizontal from the top of a 25 m high tower. The time it takes to reach the ground is (g = 10 m/s²):
सही उत्तर: ग) (1 + √6) s ≈ 3.45 s
With upward vᵧ = 10 m/s: −25 = 10t − 5t², i.e. t² − 2t − 5 = 0, so t = 1 + √6 ≈ 3.45 s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A silicon diode (cut-in 0.7 V) is forward biased by a 5 V battery through a 1 kΩ resistor. The current is:
सही उत्तर: घ) 4.3 mA
I = (5 − 0.7)/1000 = 4.3 mA.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 5 V Zener diode is fed from a 12 V supply through a 350 Ω series resistor and has a 1 kΩ load across it. The current through the Zener diode is:
सही उत्तर: क) 15 mA
Series current = (12 − 5)/350 = 20 mA; load current = 5/1000 = 5 mA; Zener current = 20 − 5 = 15 mA.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a transistor with β = 50, a base current of 40 μA flows. The emitter current is:
सही उत्तर: ख) 2.04 mA
I_C = βI_B = 2 mA, and I_E = I_C + I_B = 2.04 mA.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The output of a two-input NAND gate when both inputs are 1 is:
सही उत्तर: ख) 0
NAND = NOT(A·B); with A = B = 1, A·B = 1 so the output is 0.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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