भौतिक विज्ञान (Physics) – Physics MCQ
भौतिक विज्ञान (Physics) – CEE प्रवेश
Physics · Medical Entrance (CEE) – Physics, Chemistry, Biology & MAT · ४०७ प्रश्न
४०७ 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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A Carnot engine works between a source at 500 K and a sink at 300 K. Its efficiency is:
सही उत्तर: ख) 40%
η = 1 − T₂/T₁ = 1 − 300/500 = 0.4 = 40%. 60% is the ratio T₂/T₁ itself.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In an adiabatic process:
सही उत्तर: क) No heat is exchanged with the surroundings
Adiabatic means Q = 0, so ΔU = −W. Constant temperature, pressure and volume describe isothermal, isobaric and isochoric processes respectively.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For an ideal gas undergoing an isothermal process, the change in internal energy is:
सही उत्तर: घ) Zero
The internal energy of an ideal gas depends only on temperature, which is constant here, so ΔU = 0 and all heat supplied becomes work. In an adiabatic process it is Q, not ΔU, that is zero.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the absolute temperature of a black body is doubled, the power radiated by it becomes:
सही उत्तर: ग) 16 times
By the Stefan–Boltzmann law, P ∝ T⁴, so P becomes 2⁴ = 16 times. 4 times would be the case if P ∝ T².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Wien's displacement law states that:
सही उत्तर: ख) λₘT = constant
The wavelength of maximum emission is inversely proportional to absolute temperature, so hotter bodies glow bluer. E ∝ T⁴ is the Stefan–Boltzmann law.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A temperature of 300 K is equal to:
सही उत्तर: क) 27 °C
T(°C) = T(K) − 273 = 300 − 273 = 27 °C. 573 °C results from adding instead of subtracting.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Water flows at 2 m/s through a pipe of radius 2 cm. The speed in a narrower section of radius 1 cm is:
सही उत्तर: घ) 8 m/s
By continuity A₁v₁ = A₂v₂ and A ∝ r², so v₂ = 2 × (2/1)² = 8 m/s. 4 m/s results from using radius instead of area.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Water rises to a height of 6 cm in a capillary tube. If the radius of the tube is halved, the water will rise to:
सही उत्तर: ग) 12 cm
Capillary rise h = 2T cosθ/(rρg), so h ∝ 1/r; halving r doubles h to 12 cm. 24 cm would follow only if h ∝ 1/r².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Stokes' law, the terminal velocity of a small sphere falling through a viscous liquid is proportional to:
सही उत्तर: ख) r²
vₜ = 2r²(ρ − σ)g/9η, so vₜ ∝ r². That is why larger raindrops fall faster.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Bernoulli's theorem for a flowing ideal fluid is based on the conservation of:
सही उत्तर: क) Energy
Bernoulli's equation P + ½ρv² + ρgh = constant expresses energy conservation per unit volume. Conservation of mass gives the equation of continuity instead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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