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 absolute temperature of an ideal gas is raised from 300 K to 1200 K, its rms speed becomes:
सही उत्तर: ख) Twice
v_rms = √(3RT/M) ∝ √T; T increases 4 times so v_rms increases √4 = 2 times. Four times would be true for the average kinetic energy.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The work done by a gas in an isochoric (constant volume) process is:
सही उत्तर: क) Zero
W = ∫P dV and dV = 0, so W = 0; all heat supplied changes the internal energy. nRT ln(V₂/V₁) is the work in an isothermal process.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The ratio of specific heats γ = Cp/Cv for a monoatomic ideal gas is:
सही उत्तर: घ) 5/3
For a monoatomic gas Cv = 3R/2 and Cp = 5R/2, giving γ = 5/3. 7/5 is for a diatomic gas.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A process in which no heat enters or leaves the system is called:
सही उत्तर: ग) Adiabatic
In an adiabatic process ΔQ = 0. An isothermal process keeps temperature constant but heat may flow.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In an isothermal process for an ideal gas, the change in internal energy is:
सही उत्तर: ख) Zero
Internal energy of an ideal gas depends only on temperature; since T is constant, ΔU = 0 and all heat supplied becomes work.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which mode of heat transfer can take place through vacuum?
सही उत्तर: क) Radiation
Radiation travels as electromagnetic waves and needs no medium, which is how the Sun's heat reaches Earth. Conduction and convection require a material medium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Newton's law of cooling, the rate of cooling of a body is proportional to:
सही उत्तर: घ) The temperature difference between the body and its surroundings
Newton's law of cooling: dT/dt ∝ (T − T₀), valid for small temperature differences. The T⁴ dependence is Stefan's law for total radiation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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As the temperature of a black body increases, the wavelength at which it emits maximum radiation:
सही उत्तर: ग) Decreases
By Wien's displacement law λₘT = constant, so λₘ decreases as T rises. This is why a heated iron turns from red to white.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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While ice is melting at its melting point under normal pressure, its temperature:
सही उत्तर: ख) Remains constant
The heat supplied is used as latent heat to break the solid structure, so temperature stays at 0 °C until all ice melts.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For an isotropic solid, the coefficient of volume expansion γ and linear expansion α are related by:
सही उत्तर: क) γ = 3α
For small expansions α : β : γ = 1 : 2 : 3, so γ = 3α. β = 2α is the areal (superficial) expansion coefficient.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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