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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Using all three of three 3 Ω resistors in some combination, which of the following equivalent resistances can NOT be obtained?
सही उत्तर: क) 6 Ω
The possible values are 9 Ω (series), 1 Ω (parallel), 4.5 Ω (two in parallel + one in series) and 2 Ω (two in series, parallel with the third); 6 Ω is not possible.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A cell of emf 2 V gives a terminal voltage of 1.8 V when connected to a 9 Ω resistor. Its internal resistance is:
सही उत्तर: घ) 1 Ω
I = V/R = 1.8/9 = 0.2 A; r = (E − V)/I = 0.2/0.2 = 1 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A Van de Graaff generator builds up a very high potential mainly because:
सही उत्तर: ख) charge given to a hollow conductor moves to its outer surface
Charge transferred to the inside of a hollow conductor goes entirely to its outer surface, so charge can be added continuously and the potential keeps rising.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 12 V battery of negligible internal resistance is connected to 4 Ω and 2 Ω resistors in series. A 5 μF capacitor is connected across the 2 Ω resistor. In the steady state the charge on the capacitor is:
सही उत्तर: ग) 20 μC
In steady state no current flows into the capacitor; I = 12/6 = 2 A, so V across 2 Ω = 4 V and Q = CV = 5 μF × 4 V = 20 μC.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 1 μF capacitor discharges through a 1 MΩ resistor. The time taken for its charge to fall to half the initial value is about:
सही उत्तर: क) 0.69 s
q = q₀e^(−t/RC); q = q₀/2 when t = RC ln 2 = (10⁶ × 10⁻⁶) × 0.693 ≈ 0.69 s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A capacitor is charged through a resistor from a battery of emf E. After one time constant (t = RC), the voltage across the capacitor is about:
सही उत्तर: ख) 63% of E
V = E(1 − e^(−t/RC)); at t = RC, V = E(1 − 1/e) ≈ 0.632E.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Three identical capacitors are first connected in series and then in parallel. The ratio of the equivalent capacitances (series : parallel) is:
सही उत्तर: घ) 1 : 9
Series: C/3; parallel: 3C; ratio (C/3) : 3C = 1 : 9.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a uniformly charged non-conducting solid sphere, the ratio of the electric potential at its centre to that at its surface is:
सही उत्तर: ग) 3 : 2
Inside, V(r) = kQ(3R² − r²)/(2R³); at r = 0, V = 3kQ/(2R), while at the surface V = kQ/R, giving 3 : 2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Equal and opposite point charges +q and −q are placed a distance apart. At the midpoint between them:
सही उत्तर: ख) the electric potential is zero but the field is not
The potentials kq/r and −kq/r cancel, but the two fields both point from +q towards −q and add.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Presbyopia (difficulty in seeing both near and far objects with age) is usually corrected by:
सही उत्तर: ग) bifocal lenses
Bifocal lenses have a concave upper part for distant vision and a convex lower part for reading.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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