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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27 identical charged water drops, each at potential V, coalesce into one big drop. The potential of the big drop is:
सही उत्तर: ख) 9V
R = 3r and Q = 27q, so V′ = kQ/R = 27kq/(3r) = 9V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The electric potential at the centre of a ring of radius R carrying charge Q distributed in any manner is:
सही उत्तर: ग) Q/(4πε₀R)
Every element of charge is at the same distance R from the centre, and potential is a scalar: V = kQ/R.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The electric field at the centre of a uniformly charged semicircular ring of radius R carrying total charge Q is:
सही उत्तर: घ) Q/(2π²ε₀R²)
With λ = Q/(πR), the field is 2kλ/R = 2kQ/(πR²) = Q/(2π²ε₀R²).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Rain falls vertically at 4 m/s and a man walks horizontally at 3 m/s. To protect himself he should hold his umbrella tilted forward at an angle to the vertical of:
सही उत्तर: क) tan⁻¹(3/4) ≈ 37°
The rain's velocity relative to the man has components 4 m/s down and 3 m/s backwards, so tan θ = 3/4 from the vertical.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A stone thrown vertically upward is at the same height at t = 2 s and t = 6 s. Its speed of projection is (g = 10 m/s²):
सही उत्तर: क) 40 m/s
It reaches the top midway at t = 4 s, so u = g × 4 = 40 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Boolean expression (A + B)·(A + C) simplifies to:
सही उत्तर: ख) A + BC
Expanding: A + AC + AB + BC = A(1 + C + B) + BC = A + BC.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Roughly how many half-lives must pass for the activity of a radioactive sample to fall to one-thousandth of its initial value?
सही उत्तर: ग) 10
(1/2)ⁿ = 1/1000 gives n = log₂1000 ≈ 10 (since 2¹⁰ = 1024).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a series LCR circuit the rms voltages across R, L and C are 40 V, 60 V and 30 V. The rms supply voltage is:
सही उत्तर: घ) 50 V
V = √(V_R² + (V_L − V_C)²) = √(1600 + 900) = 50 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The energy stored per unit volume in a magnetic field B in vacuum is:
सही उत्तर: घ) B²/(2μ₀)
Magnetic energy density u = B²/(2μ₀), the counterpart of ε₀E²/2 for electric fields.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two long parallel wires 0.1 m apart in air carry currents of 2 A and 3 A. The force per unit length between them is (μ₀/2π = 2 × 10⁻⁷ T m/A):
सही उत्तर: क) 1.2 × 10⁻⁵ N/m
F/l = μ₀I₁I₂/(2πd) = 2 × 10⁻⁷ × 6/0.1 = 1.2 × 10⁻⁵ N/m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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