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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A transformer works on the principle of:
सही उत्तर: ख) Mutual induction
An alternating current in the primary produces changing flux that induces emf in the secondary (mutual induction). Hence a transformer does not work with steady DC.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The energy stored in an inductor of 2 H carrying a current of 3 A is:
सही उत्तर: क) 9 J
U = ½LI² = ½ × 2 × 9 = 9 J. 18 J comes from omitting the factor ½.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The magnetic flux through a coil of 10 turns changes by 0.5 Wb in 0.1 s. The magnitude of the average induced emf is:
सही उत्तर: घ) 50 V
ε = N ΔΦ/Δt = 10 × 0.5 / 0.1 = 50 V. 5 V is the emf per turn, ignoring the number of turns.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Above the Curie temperature, a ferromagnetic material becomes:
सही उत्तर: ख) Paramagnetic
Thermal agitation destroys the alignment of domains above the Curie temperature, so the material behaves as paramagnetic.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A substance with a small negative magnetic susceptibility is:
सही उत्तर: क) Diamagnetic
Diamagnetic materials (e.g. bismuth, copper) are weakly repelled by magnets and have small negative χ. Paramagnetic materials have small positive χ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two long parallel wires carry currents in the same direction. They:
सही उत्तर: घ) Attract each other
Parallel currents in the same direction attract, and opposite currents repel. This force was the basis of the earlier definition of the ampere.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The magnetic field at a distance of 10 cm from a long straight wire carrying a current of 10 A is (μ₀ = 4π × 10⁻⁷ T m/A):
सही उत्तर: ग) 2 × 10⁻⁵ T
B = μ₀I/(2πr) = (4π × 10⁻⁷ × 10)/(2π × 0.1) = 2 × 10⁻⁵ T. Forgetting to convert 10 cm to 0.1 m gives the wrong order of magnitude.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A charged particle of mass m and charge q moves with speed v perpendicular to a uniform magnetic field B. The radius of its circular path is:
सही उत्तर: ख) mv/(qB)
The magnetic force provides centripetal force: qvB = mv²/r, so r = mv/(qB). Faster or heavier particles move in larger circles.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A charged particle moves parallel to a uniform magnetic field. The magnetic force on it is:
सही उत्तर: क) Zero
F = qvB sinθ and θ = 0°, so F = 0. The force is maximum when the motion is perpendicular to the field.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A potentiometer is preferred over a voltmeter for measuring the emf of a cell because:
सही उत्तर: घ) It draws no current from the cell at the balance point
At balance no current flows from the cell, so the true emf (not terminal voltage) is measured. A voltmeter always draws some current.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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