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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In a photoelectric experiment, the graph of stopping potential against frequency of incident light is a straight line whose slope equals:
सही उत्तर: ख) h/e
eV₀ = hν − φ, so V₀ = (h/e)ν − φ/e and the slope is h/e.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In an LC circuit oscillating with maximum capacitor charge Q₀, the energy is shared equally between the electric and magnetic fields when the charge on the capacitor is:
सही उत्तर: क) Q₀/√2
Electric energy q²/2C equals half the total Q₀²/2C when q² = Q₀²/2, i.e. q = Q₀/√2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is an application of eddy currents?
सही उत्तर: ग) electromagnetic damping in galvanometers
Eddy currents induced in a metal former oppose its motion, bringing the coil quickly to rest (dead-beat galvanometer).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The current sensitivity of a moving-coil galvanometer (deflection per unit current) is:
सही उत्तर: ख) NAB/k
At equilibrium NIAB = kθ, so θ/I = NAB/k (N turns, area A, field B, torsion constant k).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The apparent angles of dip measured in two mutually perpendicular vertical planes are 30° and 45°. The true angle of dip is about:
सही उत्तर: क) 26.6°
cot²δ = cot²δ₁ + cot²δ₂ = 3 + 1 = 4, so tan δ = 1/2 and δ ≈ 26.6°.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A charged particle enters a uniform magnetic field B with velocity v at an angle θ to the field. The pitch of its helical path is:
सही उत्तर: ख) 2πmv cos θ/(qB)
The period is 2πm/(qB) and the velocity component along B is v cos θ, so the pitch = (v cos θ)(2πm/(qB)).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A circular loop of radius R carries a current. At a point on its axis at distance R from the centre, the magnetic field is what fraction of the field at the centre?
सही उत्तर: घ) 1/(2√2)
B_axis = μ₀IR²/[2(R² + x²)^(3/2)]; with x = R this is μ₀I/(2R) × 1/2^(3/2), i.e. 1/(2√2) of the centre value.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A thermocouple has its cold junction at 0 °C and a neutral temperature of 270 °C. Its temperature of inversion is:
सही उत्तर: क) 540 °C
The neutral temperature is the mean of the cold-junction and inversion temperatures: T_i = 2T_n − T_c = 540 °C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a fuse wire, the current at which it melts depends on its radius r but not on its length. This current is proportional to:
सही उत्तर: घ) r^(3/2)
In steady state, heat produced I²ρL/(πr²) equals heat lost ∝ 2πrL; L cancels and I² ∝ r³.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The sensitivity of a potentiometer can be increased by:
सही उत्तर: क) increasing the length of the potentiometer wire
A longer wire (with the same driving cell) gives a smaller potential gradient, so a given emf corresponds to a longer balancing length.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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