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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Cells of emf 6 V and 4 V, each of internal resistance 1 Ω, are connected in series opposing each other with an external resistance of 3 Ω. The current is:
सही उत्तर: घ) 0.4 A
Net emf = 6 − 4 = 2 V, total resistance = 1 + 1 + 3 = 5 Ω, so I = 0.4 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A dielectric slab of constant K completely fills the gap of a parallel-plate capacitor that remains connected to a battery. The charge on the capacitor:
सही उत्तर: क) becomes K times
With the battery connected V is fixed, and C becomes KC, so Q = CV becomes K times.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Three capacitors of 6 μF each are available. Two are connected in series and the third is connected in parallel with this pair. The equivalent capacitance is:
सही उत्तर: ख) 9 μF
Series pair = 3 μF; adding 6 μF in parallel gives 9 μF.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Charges of +2 μC and −2 μC are 20 cm apart in air. The electric field at the midpoint between them is (k = 9 × 10⁹ N m² C⁻²):
सही उत्तर: ख) 3.6 × 10⁶ N/C
Each charge gives kq/r² = 9 × 10⁹ × 2 × 10⁻⁶/0.01 = 1.8 × 10⁶ N/C, and the two fields point the same way (towards −q), so E = 3.6 × 10⁶ N/C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two point charges in air repel with a force F. When the same arrangement is placed in a medium of dielectric constant 4, the force becomes:
सही उत्तर: क) F/4
F = q₁q₂/(4πε₀Kr²), so the force is reduced by the factor K = 4.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A long-sighted person has a near point of 50 cm. The power of the lens needed to read at 25 cm is:
सही उत्तर: घ) +2 D
1/f = 1/v − 1/u = 1/(−0.5) − 1/(−0.25) = 2 m⁻¹, so P = +2 D (convex lens).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For relaxed viewing (normal adjustment), how far apart must the 150 cm objective and the 5 cm eyepiece of a refracting astronomical telescope be placed?
सही उत्तर: ग) 155 cm
In normal adjustment L = f₀ + fₑ = 150 + 5 = 155 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A compound microscope has an objective that forms an image magnified 10 times, and an eyepiece of focal length 5 cm. With the final image at the least distance of distinct vision (25 cm), the total magnifying power is:
सही उत्तर: ग) 60
Eyepiece: 1 + D/fₑ = 1 + 25/5 = 6; total M = 10 × 6 = 60.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Unpolarised light of intensity I₀ passes through three polarisers whose axes are at 0°, 45° and 90° in turn. The intensity of the emerging light is:
सही उत्तर: क) I₀/8
After the 1st: I₀/2; after the 2nd: (I₀/2)cos²45° = I₀/4; after the 3rd: (I₀/4)cos²45° = I₀/8.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Light of wavelength 500 nm falls on a slit 0.1 mm wide, and the diffraction pattern is seen on a screen 1 m away. The width of the central maximum is:
सही उत्तर: घ) 10 mm
Width = 2λD/a = 2 × 500 × 10⁻⁹ × 1/10⁻⁴ = 10⁻² m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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