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 Kelvin–Planck statement of the second law of thermodynamics implies that:
सही उत्तर: ख) no heat engine working in a cycle can convert all the heat absorbed into work
It forbids a cyclic engine with 100% efficiency; some heat must be rejected to a sink.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The number of degrees of freedom of a rigid diatomic gas molecule (at ordinary temperature) is:
सही उत्तर: ग) 5
It has 3 translational and 2 rotational degrees of freedom; vibration is not excited at ordinary temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The average translational kinetic energy of a gas molecule at absolute temperature T is (k = Boltzmann constant):
सही उत्तर: ग) (3/2)kT
Each of the three translational degrees of freedom contributes ½kT, giving (3/2)kT.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When the frequency of light falling on a photosensitive surface is doubled (above threshold), the maximum kinetic energy of the emitted photoelectrons becomes:
सही उत्तर: क) more than double
K = hν − φ, so the new K′ = 2hν − φ = 2K + φ, which is more than 2K.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When a gas is compressed suddenly (adiabatically), its temperature:
सही उत्तर: ख) increases
In an adiabatic compression no heat escapes, so the work done on the gas raises its internal energy and temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The ratio of specific heats γ = Cp/Cv for a diatomic ideal gas (at room temperature) is:
सही उत्तर: घ) 7/5
For a diatomic gas with 5 degrees of freedom, Cv = 5R/2 and Cp = 7R/2, so γ = 7/5 = 1.4.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a series LCR circuit, R = 30 Ω, X_L = 30 Ω and X_C = 70 Ω. The impedance of the circuit is:
सही उत्तर: क) 50 Ω
Z = √(R² + (X_C − X_L)²) = √(900 + 1600) = 50 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A proton and an alpha particle with the same kinetic energy move perpendicular to the same uniform magnetic field. The ratio of the radius of the alpha particle's path to that of the proton is:
सही उत्तर: क) 1 : 1
r = √(2mK)/(qB); the alpha has 4 times the mass and 2 times the charge, so r_α/r_p = √4/2 = 1.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Wien's displacement law, if the absolute temperature of a black body is doubled, the wavelength of maximum emission:
सही उत्तर: क) becomes half
λ_max T = constant, so λ_max ∝ 1/T.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a metre bridge, an unknown resistance X is in the left gap and 6 Ω in the right gap. The balance point is 40 cm from the left end. X is:
सही उत्तर: ग) 4 Ω
X/6 = 40/60, so X = 4 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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