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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If the rms speed of the molecules of a gas in a closed vessel of fixed volume is doubled, its pressure becomes:
सही उत्तर: घ) four times
P = ⅓ρv²_rms with ρ fixed, so doubling v_rms makes P four times.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The value of the Boltzmann constant k is about:
सही उत्तर: ग) 1.38 × 10⁻²³ J K⁻¹
k = R/N_A = 8.314/(6.022 × 10²³) ≈ 1.38 × 10⁻²³ J K⁻¹.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For the molecules of a gas at a given temperature, the most probable speed (v_mp), average speed (v_av) and rms speed (v_rms) are related as:
सही उत्तर: क) v_mp < v_av < v_rms
They are in the ratio √2 : √(8/π) : √3 ≈ 1.41 : 1.60 : 1.73.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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One mole of a monatomic ideal gas is mixed with one mole of a diatomic ideal gas. The ratio Cp/Cv for the mixture is:
सही उत्तर: ग) 1.5
Cv(mix) = (3/2 R + 5/2 R)/2 = 2R and Cp = Cv + R = 3R, so γ = 3R/2R = 1.5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The work done by an ideal gas in a reversible adiabatic expansion from state (P₁, V₁) to (P₂, V₂) is:
सही उत्तर: ग) (P₁V₁ − P₂V₂)/(γ − 1)
For an adiabatic process W = ∫P dV = (P₁V₁ − P₂V₂)/(γ − 1), which is positive for expansion.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The internal energy of a given mass of an ideal gas depends only on its:
सही उत्तर: घ) temperature
An ideal gas has no intermolecular forces, so its internal energy is purely kinetic and depends only on temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a natural (irreversible) process, the total entropy of the universe:
सही उत्तर: ग) increases
By the second law, the entropy of an isolated system (the universe) increases in every irreversible process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Heat is supplied to a monatomic ideal gas at constant pressure. The fraction of this heat that goes into increasing its internal energy is:
सही उत्तर: क) 3/5
ΔU/Q = nCvΔT/(nCpΔT) = Cv/Cp = (3/2 R)/(5/2 R) = 3/5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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At any point, the slope of an adiabatic curve on a P–V diagram is related to the slope of the isothermal curve through the same point by:
सही उत्तर: ग) adiabatic slope = γ × isothermal slope
Isothermal: dP/dV = −P/V; adiabatic: dP/dV = −γP/V; so the adiabatic is γ times steeper.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The zeroth law of thermodynamics leads to the concept of:
सही उत्तर: घ) temperature
If two bodies are each in thermal equilibrium with a third, they are in equilibrium with each other; the common property is temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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