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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If the frequency of an AC supply is doubled, the reactance of a capacitor connected to it becomes:
सही उत्तर: ग) half
X_C = 1/(2πfC), so doubling f halves X_C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Curie's law, the magnetic susceptibility χ of a paramagnetic substance varies with absolute temperature T as:
सही उत्तर: ख) χ ∝ 1/T
Curie's law: χ = C/T, because thermal agitation opposes the alignment of atomic dipoles.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The angle of dip at the Earth's magnetic equator is:
सही उत्तर: क) 0°
At the magnetic equator the Earth's field is horizontal, so the dip is 0°; it is 90° at the magnetic poles.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A rectangular coil of 10 turns and area 0.01 m² carries 2 A in a uniform field of 0.5 T, with its plane parallel to the field. The torque on it is:
सही उत्तर: घ) 0.1 N m
τ = NIAB sin θ, where θ = 90° between the field and the coil's normal: 10 × 2 × 0.01 × 0.5 = 0.1 N m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An electron moves at 1 × 10⁶ m/s perpendicular to a magnetic field of 0.5 T. The magnetic force on it is (e = 1.6 × 10⁻¹⁹ C):
सही उत्तर: ग) 8 × 10⁻¹⁴ N
F = evB sin 90° = 1.6 × 10⁻¹⁹ × 10⁶ × 0.5 = 8 × 10⁻¹⁴ N.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A galvanometer can be converted into a voltmeter by connecting:
सही उत्तर: ख) a high resistance in series
A large series resistance limits the current to the galvanometer's full-scale value while it measures potential difference.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Kirchhoff's voltage (loop) law is based on the conservation of:
सही उत्तर: क) energy
Around a closed loop the net work done per unit charge is zero, so the sum of emfs equals the sum of potential drops; this is energy conservation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The drift speed v_d of electrons in a conductor of cross-section A carrying current I (n = free electron density, e = electronic charge) is:
सही उत्तर: घ) I/(neA)
Current I = neAv_d, so v_d = I/(neA).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A point charge q is placed at the centre of a cube. The electric flux through any one face of the cube is:
सही उत्तर: ग) q/(6ε₀)
The total flux q/ε₀ is shared equally by the six symmetric faces, giving q/(6ε₀) per face.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The electric field near an infinite plane sheet of charge with uniform surface charge density σ is:
सही उत्तर: ख) σ/(2ε₀)
A Gaussian pillbox through the sheet has two faces: 2EA = σA/ε₀, so E = σ/(2ε₀), independent of distance.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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