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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Hubble's law states that the recessional velocity v of a distant galaxy and its distance d are related by:
सही उत्तर: ख) v = H₀d
Galaxies recede with speeds proportional to their distances, v = H₀d, which is evidence for an expanding universe.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two long coaxial solenoids of length l have n₁ and n₂ turns per unit length, and the inner one has cross-sectional area A. Their mutual inductance is:
सही उत्तर: ख) μ₀n₁n₂Al
Current I in the outer solenoid gives B = μ₀n₁I; the flux through the n₂l turns of the inner one is μ₀n₁I·A·n₂l, so M = μ₀n₁n₂Al.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the same power is transmitted over a line at a higher voltage, the power loss in the line resistance:
सही उत्तर: ग) decreases in inverse proportion to the square of the voltage
For power P = VI, the current is I = P/V, so the loss I²R = P²R/V² falls as 1/V².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a series LR circuit connected to an AC source, the phase angle φ by which the current lags the voltage is given by:
सही उत्तर: ख) tan φ = ωL/R
The voltage phasors across R and L are at 90°, so tan φ = V_L/V_R = ωL/R.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The average value of a sinusoidal alternating current of peak value I₀, taken over one half-cycle, is:
सही उत्तर: घ) 2I₀/π (≈ 0.637 I₀)
Average over a half-cycle = (1/π)∫₀^π I₀ sin θ dθ = 2I₀/π; over a full cycle the average is zero.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The angle between the geographic meridian and the magnetic meridian at a place is called the:
सही उत्तर: क) angle of declination
Declination measures how far a compass needle deviates from true north; dip is the angle the Earth's field makes with the horizontal.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The magnetic field at the centre of a circular arc of radius r that subtends an angle θ (radians) at the centre and carries current I is:
सही उत्तर: घ) μ₀Iθ/(4πr)
From the Biot–Savart law each element contributes μ₀I dl/(4πr²); summing over arc length rθ gives μ₀Iθ/(4πr) (θ = 2π gives μ₀I/2r for a full loop).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Hall voltage across a conducting strip of thickness t carrying current I in a perpendicular magnetic field B (n = carrier density, e = carrier charge) is:
सही उत्तर: घ) BI/(net)
In equilibrium eE_H = ev_dB with v_d = I/(neA); the Hall voltage V_H = E_H × width works out to BI/(net).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a tangent galvanometer, the current I is related to the deflection θ of the needle by:
सही उत्तर: ख) I ∝ tan θ
In equilibrium the coil's field B = B_H tan θ, and B ∝ I, so I = K tan θ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An electron revolves in a circular orbit of radius r with speed v. The magnetic moment of this current loop is:
सही उत्तर: ग) evr/2
The current is I = e/T = ev/(2πr) and the area is πr², so μ = IA = evr/2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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