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 SI unit of luminous intensity is:
सही उत्तर: क) Candela
Candela is one of the seven SI base units and measures luminous intensity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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With increase in temperature, the electrical resistance of a pure (intrinsic) semiconductor:
सही उत्तर: ग) Decreases
Higher temperature breaks more covalent bonds, generating more electron–hole pairs, so conductivity rises and resistance falls. Semiconductors therefore have a negative temperature coefficient of resistance.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a common-emitter transistor, the base current is 50 μA and the collector current is 5 mA. The current gain β is:
सही उत्तर: ख) 100
β = I_C / I_B = 5 × 10⁻³ / 50 × 10⁻⁶ = 100. 1000 results from a unit-conversion error between mA and μA.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A p–n junction diode used to convert AC into DC acts as a:
सही उत्तर: क) Rectifier
A diode conducts only in forward bias, allowing current in one direction, which converts AC to pulsating DC (rectification).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following logic gates is a universal gate?
सही उत्तर: घ) NAND
Any logic gate can be built using only NAND gates (or only NOR gates). OR, AND and XOR alone cannot produce all functions.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A Zener diode is mainly used as a:
सही उत्तर: ग) Voltage regulator
Operated in reverse breakdown, a Zener diode keeps the voltage across it almost constant despite changes in current. A transistor, not a Zener, is used as an amplifier.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The majority charge carriers in an n-type semiconductor are:
सही उत्तर: ख) Electrons
Pentavalent donor atoms contribute extra free electrons, which become majority carriers. Holes are the minority carriers in n-type material.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A p-type semiconductor is formed by doping pure silicon with a:
सही उत्तर: क) Trivalent impurity such as boron
Trivalent atoms create holes (acceptors), making holes the majority carriers. Pentavalent dopants give n-type semiconductors.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Nuclear fission of uranium-235 in a reactor is initiated by:
सही उत्तर: घ) Slow (thermal) neutrons
U-235 has a large fission cross-section for slow neutrons, which is why reactors use moderators. Fission releases about 200 MeV per nucleus.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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X-rays were discovered by:
सही उत्तर: ग) Wilhelm Röntgen
Röntgen discovered X-rays in 1895 while working with cathode-ray tubes. Becquerel discovered radioactivity in 1896.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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