विज्ञान – Science MCQ
विज्ञान – डिप्लोमा प्रवेश
Science · CTEVT Diploma Engineering Entrance · ४०५ प्रश्न
४०५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
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 bicycle dynamo lights a lamp when the wheel turns. It works on the principle of:
सही उत्तर: ख) Electromagnetic induction
Rotating a magnet near a coil changes the magnetic flux and induces a current (electromagnetic induction). An electric motor, in contrast, converts electrical energy into mechanical energy.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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To find the direction of force on a current-carrying conductor placed in a magnetic field (as in an electric motor), we use:
सही उत्तर: क) Fleming's left-hand rule
Fleming's left-hand rule gives the direction of force in motors. The right-hand rule is used for the direction of induced current in generators.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A transformer has 200 turns in the primary and 1000 turns in the secondary. If the input is 220 V AC, the output voltage is:
सही उत्तर: घ) 1100 V
Vs/Vp = Ns/Np, so Vs = 220 × 1000/200 = 1100 V; it is a step-up transformer. 44 V would result from inverting the turns ratio.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A current of 2 A flows through a wire for 1 minute. The charge passing through it is:
सही उत्तर: क) 120 C
Q = I × t = 2 × 60 = 120 C. Time must be converted to seconds; using t = 1 gives the wrong answer 2 C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Four bulbs of 60 W each are used for 5 hours. The electrical energy consumed is:
सही उत्तर: क) 1.2 kWh
Energy = 4 × 60 W × 5 h = 1200 Wh = 1.2 kWh. 1200 is the value in Wh, not kWh.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 1000 W heater is used for 3 hours daily for 30 days. If electricity costs Rs 10 per unit, the cost is:
सही उत्तर: घ) Rs 900
Energy = 1 kW × 3 h × 30 = 90 kWh (units); cost = 90 × 10 = Rs 900. Rs 90 is the number of units, not the cost.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A bulb draws 0.5 A when connected to a 220 V supply. Its power is:
सही उत्तर: ख) 110 W
P = VI = 220 × 0.5 = 110 W. 440 comes from dividing 220 by 0.5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two 6 Ω resistors are connected in parallel. The equivalent resistance is:
सही उत्तर: क) 3 Ω
1/R = 1/6 + 1/6 = 1/3, so R = 3 Ω. For n equal resistors in parallel, R = R/n; 12 Ω would be the series value.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Resistors of 2 Ω, 3 Ω and 5 Ω are connected in series. The equivalent resistance is:
सही उत्तर: ग) 10 Ω
In series, R = R₁ + R₂ + R₃ = 2 + 3 + 5 = 10 Ω. About 0.97 Ω would be the parallel combination.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 12 V battery is connected across a 4 Ω resistor. The current through it is:
सही उत्तर: घ) 3 A
By Ohm's law I = V/R = 12/4 = 3 A. 48 comes from wrongly multiplying V and R.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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