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
-
The function of a moderator in a nuclear reactor is to:
सही उत्तर: ख) Slow down fast neutrons
Moderators like heavy water or graphite slow neutrons so they can efficiently cause fission of U-235. Absorbing neutrons is the job of control rods (e.g. cadmium, boron).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
Cathode rays consist of:
सही उत्तर: क) Electrons
J. J. Thomson showed that cathode rays are streams of negatively charged particles, later called electrons, as they are deflected by electric and magnetic fields.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
In β⁻ decay, the atomic number and mass number of the nucleus respectively:
सही उत्तर: घ) Increase by 1 and remain unchanged
A neutron changes into a proton emitting an electron (and an antineutrino), so Z increases by 1 while A stays the same. Decrease by 2 and 4 describes alpha decay.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
An alpha particle is:
सही उत्तर: ग) A helium nucleus
An alpha particle consists of 2 protons and 2 neutrons (⁴₂He nucleus). A beta particle is an electron, and a gamma ray is a photon.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
In Bohr's model, the radius of the n = 2 orbit of hydrogen compared to the n = 1 orbit is:
सही उत्तर: ख) Four times
rₙ = r₁n², so r₂ = 4r₁. The energy, by contrast, varies as 1/n².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
Light of photon energy 5 eV falls on a metal of work function 2 eV. The stopping potential is:
सही उत्तर: ग) 3 V
K_max = 5 − 2 = 3 eV, so the stopping potential V₀ = K_max/e = 3 V. 7 V results from adding instead of subtracting the work function.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
As the frequency of an AC source increases, the reactance of a capacitor:
सही उत्तर: ख) Decreases
X_C = 1/(2πfC), so it decreases with frequency; that is why a capacitor blocks DC (f = 0) but passes high-frequency AC. Inductive reactance increases with frequency.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
The resonant frequency of a series LCR circuit is:
सही उत्तर: क) 1/(2π√(LC))
At resonance X_L = X_C, i.e. ωL = 1/(ωC), giving ω = 1/√(LC) and f = 1/(2π√(LC)). At resonance the impedance equals R.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
The peak value of an AC voltage is 311 V. Its rms value is approximately:
सही उत्तर: घ) 220 V
V_rms = V₀/√2 = 311/1.414 ≈ 220 V. 155 V is V₀/2, which is not the rms value.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
-
The core of a transformer is laminated in order to reduce:
सही उत्तर: ग) Eddy current losses
Thin insulated laminations increase resistance to eddy currents circulating in the core, reducing heat loss. Copper losses are due to resistance of the windings.
💬 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।
नमस्ते! पाठ्यक्रम, सामान्य ज्ञान, भाषा परीक्षा वा कुनै प्रश्नको उत्तर बुझ्न सोध्नुहोस्।
AI ले गल्ती गर्न सक्छ। महत्वपूर्ण कुरा आधिकारिक स्रोतमा जाँच्नुहोस्।