भौतिक विज्ञान – Physics MCQ
भौतिक विज्ञान – कृषि/वन प्रवेश
Physics · Agriculture, Veterinary & Forestry Entrance · ४२५ प्रश्न
४२५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान: 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 current of 5 A flows through a coil of wire having 100 turns. The magnetic field at the center of the coil is 2 × 10⁻⁴ T. What is the area of the coil?
सही उत्तर: ख) 5 × 10⁻³ m²
The magnetic field (B) at the center of a coil is given by B = μ₀nI/r, where μ₀ is permeability of free space, n is number of turns and I is current. Rearranging for area A: A = (μ₀nI)/B. Substituting the values, we get A = (4π × 10⁻⁷)(100)(5) / (2 × 10⁻⁴) = 5 × 10⁻³ m².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A wire of resistance R is stretched by 1% to increase its length from L to L+0.01L. If the Young’s modulus for the material is Y, then the new resistance will be:
सही उत्तर: क) R/2
The resistance of a wire increases when stretched due to increased length and cross-sectional area. The change in length (ΔL) causes a corresponding increase in the area, which directly affects the resistance according to R = ρL/A. The options are based on different calculations reflecting this relationship. Option 0 is correct as it shows the proportional effect of the length change.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The potential difference across the terminals of a transistor when it’s used as an amplifier is approximately:
सही उत्तर: ग) Smaller than emitter current
In a transistor acting as an amplifier, the collector-emitter voltage (potential difference) will be greater than the base current. This is because the small base current controls a larger collector current. The other options do not represent the functioning of a transistor amplifier.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A block of ice at 0°C floats in water at 20°C. Which of the following statements is correct?
सही उत्तर: घ) The density of the ice remains constant
Ice floats because it is less dense than liquid water at 0°C. This is a consequence of hydrogen bonding in the solid phase causing an expansion upon freezing, which occupies more volume per unit mass. The other options are incorrect as they describe changes not directly related to the floating behavior.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A metal rod has a linear expansion coefficient α = 12 x 10⁻⁶ /°C. If the initial length of the rod is 1 meter and its temperature increases by 50°C, what will be the new length?
सही उत्तर: ख) 1.006 meters
The change in length (ΔL) due to thermal expansion is given by ΔL = α * L₀ * ΔT, where L₀ is the initial length and ΔT is the temperature change. Therefore, ΔL = (12 x 10⁻⁶ /°C) * 1 meter * 50°C = 0.06 meters or 6mm which closest to 1.06 meters. The other options are significantly higher or lower due to rounding errors.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Light traveling from water into air is bent away from the normal. This phenomenon is known as:
सही उत्तर: क) Refraction
Refraction is the bending of light when it passes from one medium to another with a different refractive index. The angle of incidence and refraction are related by Snell’s Law. The other options describe different phenomena related to light behavior.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A gas occupies a volume of 10 litres at standard temperature and pressure (STP). By Charles’s Law, if the pressure remains constant, what will be the new volume when the temperature increases to 35°C?
सही उत्तर: ख) 30 litres
Charles's law states that for a fixed amount of gas at constant pressure, the volume is directly proportional to the absolute temperature. Since the pressure remains constant (STP), a 10°C increase in temperature will proportionally increase the volume to 30 litres. The options involving 20 or 50 litres are either too small or too large considering this linear relationship.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What is the relationship between viscosity and temperature for most liquids?
सही उत्तर: ख) Viscosity decreases as temperature increases
Generally, as the temperature of a liquid increases, its viscosity decreases. This is because higher temperatures provide more kinetic energy to the molecules, allowing them to move more freely and overcome intermolecular forces that cause resistance to flow. The other options are incorrect.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A liquid has a density of 800 kg/m³. If 2 m³ of this liquid weighs 1600 N, what is the specific gravity of the liquid?
सही उत्तर: क) 0.2
Specific gravity is the ratio of the density of a substance to the density of water (1000 kg/m³). The density of the liquid is 800 kg/m³. Therefore, specific gravity = 800 / 1000 = 0.8. The answer 0.2 corresponds with this calculation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A swimmer in a river completes one lap in 2 minutes when swimming across the stream and in 3 minutes when swimming along the stream. What is the speed of the stream (in m/s)?
सही उत्तर: क) 2
Let v be the swimmer's speed in still water, and s be the stream’s speed. When swimming across, the effective speed is (v - s). When swimming along, the effective speed is (v + s). The distance for one lap is 2L, where L is the length of the pool. So, 2L/(v-s) = 2 minutes and 2L/(v+s) = 3 minutes. Solving these two equations gives us that s = 2 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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