आधारभूत विद्युत् (Basic Electrical) – Basic Electrical Engineering MCQ
आधारभूत विद्युत् (Basic Electrical) – इलेक्ट्रिकल र टेलिकम
Basic Electrical Engineering · Technical – Electrical, Mechanical & Telecom · २,२९९ प्रश्न
२,२९९ प्रश्न उपलब्ध। मोड छान्नुहोस्:
आधारभूत विद्युत् (Basic Electrical): 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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Six cells, each of emf 2 V and internal resistance 1 Ω, are to send the largest current through an external resistance of 1.5 Ω. The best arrangement is:
सही उत्तर: ख) 2 parallel rows of 3 cells in series
Maximum current occurs when the internal resistance equals the external one: 2 rows of 3 give r = 3/2 = 1.5 Ω and I = 6/3 = 2 A, more than the other arrangements.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 2 Ω resistor is connected in series with a parallel combination of 6 Ω and (1 Ω + 2 Ω in series). The total resistance is:
सही उत्तर: ग) 4 Ω
1 Ω + 2 Ω = 3 Ω; 6 ∥ 3 = 2 Ω; total = 2 + 2 = 4 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 6 V, 3 W lamp is to be operated from a 24 V supply. The resistance that must be connected in series with it is:
सही उत्तर: घ) 36 Ω
Lamp current = 3/6 = 0.5 A; the resistor must drop 18 V, so R = 18/0.5 = 36 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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What resistance must be connected in parallel with a 12 Ω resistor to obtain an equivalent resistance of 4 Ω?
सही उत्तर: ख) 6 Ω
1/X = 1/4 − 1/12 = 2/12, so X = 6 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A current of 14 A divides among three parallel resistors of 1 Ω, 2 Ω and 4 Ω. The current in the 2 Ω resistor is:
सही उत्तर: घ) 4 A
Branch currents are proportional to conductances 1 : 0.5 : 0.25; the 2 Ω share is 14 × 0.5/1.75 = 4 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A four-band resistor reads violet, green, black, silver. Its value and tolerance are:
सही उत्तर: क) 75 Ω ± 10%
Violet = 7, green = 5, black multiplier = 10⁰ → 75 Ω; silver tolerance = ±10%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A resistor carries the colour bands grey, red, green (first three bands). Its nominal value is:
सही उत्तर: ग) 8.2 MΩ
Grey = 8, red = 2, green multiplier = 10⁵: 82 × 10⁵ Ω = 8.2 MΩ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The insulation resistance of a single-core cable of length l, conductor radius r₁, insulation outer radius r₂ and insulation resistivity ρ is:
सही उत्तर: घ) (ρ/2πl) ln(r₂/r₁)
The leakage current flows radially through cylindrical shells: dR = ρ dr/(2πrl), which integrates to (ρ/2πl) ln(r₂/r₁); it therefore falls as the length increases.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A copper resistor (α = +0.004 /°C) is joined in series with a carbon resistor (α = −0.0005 /°C) so that the total resistance does not change with temperature. The ratio R_carbon : R_copper must be:
सही उत्तर: ग) 8 : 1
Changes cancel when R_cu × 0.004 = R_c × 0.0005, giving R_c/R_cu = 8.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A conductor has α₀ = 0.004 /°C (referred to 0 °C). Its temperature coefficient referred to 50 °C is:
सही उत्तर: ख) 1/300 per °C
α₅₀ = α₀/(1 + α₀ × 50) = 0.004/1.2 = 1/300 ≈ 0.00333 per °C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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