भौतिक विज्ञान – Physics MCQ
भौतिक विज्ञान – कृषि/वन प्रवेश
Physics · Agriculture, Veterinary & Forestry Entrance · ४२५ प्रश्न
४२५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान: 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 efficiency of a Carnot engine working between a source at 500 K and a sink at 300 K is:
सही उत्तर: क) 40%
η = 1 − T₂/T₁ = 1 − 300/500 = 0.4 = 40%. 60% is the ratio T₂/T₁, not the efficiency.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A gas has a volume of 2 L at 300 K. If it is heated to 600 K at constant pressure, its volume becomes:
सही उत्तर: ख) 4 L
Charles's law: V ∝ T (in kelvin), so doubling T from 300 K to 600 K doubles the volume to 4 L.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A gas occupies 3 L at a pressure of 2 atm. If the pressure is increased to 6 atm at constant temperature, the new volume is:
सही उत्तर: क) 1 L
Boyle's law: P₁V₁ = P₂V₂, so V₂ = 2 × 3/6 = 1 L. 9 L would come from wrongly assuming volume increases with pressure.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Wien's displacement law, as the temperature of a hot body increases, the wavelength of maximum emission:
सही उत्तर: घ) Decreases
λₘT = constant, so λₘ shifts to shorter wavelengths at higher temperature. That is why a heated iron glows red first and then white.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Stefan's law, if the absolute temperature of a black body is doubled, the energy radiated per second becomes:
सही उत्तर: ख) 16 times
Stefan's law: E ∝ T⁴, so doubling T gives 2⁴ = 16 times the radiated power.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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At which temperature do the Celsius and Fahrenheit scales show the same reading?
सही उत्तर: ग) −40°
Setting C = F in F = 9C/5 + 32 gives C = −40. At 0 °C the Fahrenheit reading is 32 °F.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Normal human body temperature of 98.6 °F is equal to:
सही उत्तर: ख) 37 °C
C = (F − 32) × 5/9 = 66.6 × 5/9 = 37 °C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Absolute zero temperature on the Celsius scale is:
सही उत्तर: घ) −273.15 °C
0 K = −273.15 °C, the lowest possible temperature. 0 °C is the melting point of ice (273.15 K).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A hydraulic lift (or hydraulic brake) works on the principle of:
सही उत्तर: ग) Pascal's law
Pascal's law says pressure applied to an enclosed fluid is transmitted equally in all directions, so a small force on a small piston gives a large force on a large piston.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When a glass capillary tube is dipped in mercury, the mercury level inside the tube:
सही उत्तर: ग) Falls below the outside level
Mercury does not wet glass (obtuse angle of contact), so it is depressed in the capillary. Water, which wets glass, rises instead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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