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 energy of the Sun is produced mainly by:
सही उत्तर: क) Nuclear fusion
In the Sun's core, hydrogen nuclei fuse to form helium, releasing energy. Fission (splitting heavy nuclei) is used in nuclear power reactors.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which radiation has the greatest penetrating power?
सही उत्तर: ग) Gamma rays
Gamma rays are uncharged high-energy electromagnetic waves and penetrate the most. Alpha particles are the least penetrating and are stopped by paper.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When a nucleus emits a beta particle (β⁻), its atomic number:
सही उत्तर: ख) Increases by 1
In β⁻ decay a neutron changes into a proton and an electron, so Z increases by 1 while mass number stays the same. Alpha emission decreases Z by 2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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After three half-lives, the fraction of a radioactive sample that remains undecayed is:
सही उत्तर: घ) 1/8
Each half-life halves the amount: (1/2)³ = 1/8. Thus 7/8 of the sample has decayed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The energy of an electron in the ground state of a hydrogen atom is:
सही उत्तर: ख) −13.6 eV
Eₙ = −13.6/n² eV; for n = 1 it is −13.6 eV. −3.4 eV is the energy of the first excited state (n = 2).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the photoelectric effect, the maximum kinetic energy of emitted electrons depends on the:
सही उत्तर: ख) Frequency of incident light
Einstein's equation KE_max = hf − φ shows dependence on frequency. Intensity changes only the number of electrons emitted, not their maximum energy.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is a ferromagnetic substance?
सही उत्तर: क) Nickel
Iron, cobalt and nickel are ferromagnetic. Aluminium is paramagnetic, while copper and bismuth are diamagnetic.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A transformer has 100 turns in the primary and 500 turns in the secondary. If the primary voltage is 220 V AC, the secondary voltage is:
सही उत्तर: ख) 1100 V
Vs/Vp = Ns/Np, so Vs = 220 × 500/100 = 1100 V (step-up). 44 V results from inverting the turns ratio.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Lenz's law, which gives the direction of induced current, is a consequence of the conservation of:
सही उत्तर: क) Energy
The induced current opposes the change that produces it; otherwise energy would be created from nothing. Faraday's law gives the magnitude of induced emf.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The force on a charged particle moving parallel to a uniform magnetic field is:
सही उत्तर: ग) Zero
F = qvB sinθ and θ = 0° gives sin0° = 0. The force is maximum (qvB) when motion is perpendicular to the field.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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