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 bar magnet of moment M is placed at an angle θ to a uniform magnetic field B. The torque on it is:
सही उत्तर: ख) MB sin θ
τ = M × B, of magnitude MB sin θ, tending to align the magnet with the field.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The magnetic field at a distance r on the axial line of a short bar magnet of moment M is:
सही उत्तर: ख) (μ₀/4π)(2M/r³)
On the axial (end-on) line B = (μ₀/4π)(2M/r³); on the equatorial line it is half of this.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The absorption or evolution of heat along a single conductor whose parts are at different temperatures, when a current flows through it, is called the:
सही उत्तर: क) Thomson effect
The Thomson effect concerns a single conductor with a temperature gradient; the Peltier effect occurs at a junction of two different metals.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A current of 2 A is passed through copper sulphate solution for 1000 s. If the electrochemical equivalent of copper is 3.3 × 10⁻⁷ kg/C, the mass of copper deposited is:
सही उत्तर: क) 0.66 g
By Faraday's first law, m = ZIt = 3.3 × 10⁻⁷ × 2 × 1000 = 6.6 × 10⁻⁴ kg = 0.66 g.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The microscopic (point) form of Ohm's law is:
सही उत्तर: ग) J = σE
Current density J is proportional to the field: J = σE, where σ is the conductivity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The mobility of charge carriers in a conductor is defined as:
सही उत्तर: क) drift velocity per unit electric field
μ = v_d/E, measured in m² V⁻¹ s⁻¹.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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One heater coil boils a kettle of water in 10 minutes and another in 15 minutes on the same supply. With the two coils connected in series on that supply, the time taken is:
सही उत्तर: क) 25 minutes
For fixed heat H = V²t/R, t ∝ R. In series R = R₁ + R₂, so t = t₁ + t₂ = 25 minutes (in parallel it would be t₁t₂/(t₁ + t₂) = 6 min).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An electron enters a uniform electric field with a velocity perpendicular to the field. Its path inside the field is:
सही उत्तर: घ) a parabola
It has constant velocity perpendicular to the field and constant acceleration along it, like a horizontally thrown projectile.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Outside a uniformly charged thin spherical shell, the electric field is:
सही उत्तर: घ) the same as if the whole charge were concentrated at its centre
By Gauss's law, for r > R, E = Q/(4πε₀r²), as for a point charge at the centre.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The electric potential at a point at distance r from a short dipole of moment p, along a direction making angle θ with the dipole axis, is:
सही उत्तर: ग) p cos θ/(4πε₀r²)
V = (1/4πε₀)(p cos θ/r²); it is maximum on the axis and zero on the equatorial line.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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