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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If a charge of 450 Coulombs passes, what was the duration of the current flow in seconds?
सही उत्तर: ख) 25 s
Q = It, therefore, t = Q/I = 450 / 18 = 25 s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Three equal capacitors C connected in delta are to be replaced by an equivalent star. Each star-connected capacitor must be:
सही उत्तर: घ) 3C
Capacitive admittance is proportional to C, so the delta-to-star rule for admittances gives Y_star = 3Y_delta, i.e. 3C (the reverse of resistors, where R_star = R_delta/3).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 100 Ω resistor is measured by the ammeter–voltmeter method with the voltmeter (1 kΩ) connected directly across the resistor and the ammeter outside it. The value V/I obtained is about:
सही उत्तर: क) 90.9 Ω
The ammeter also reads the voltmeter current, so V/I equals R ∥ R_V = 100 × 1000/1100 ≈ 90.9 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A circuit has v = 100 sin(ωt + 30°) V and i = 5 sin(ωt − 30°) A. Its resistance and reactance are:
सही उत्तर: ग) R = 10 Ω, X = 17.3 Ω (inductive)
Z = (100/5)∠(30° − (−30°)) = 20∠60° = 10 + j17.3 Ω; the current lags, so the reactance is inductive.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A single-phase 230 V load of 20 A is fed by a two-core copper cable 30 m long (ρ = 1.72 × 10⁻⁸ Ω·m). For a voltage drop of at most 3%, the minimum conductor cross-section is about:
सही उत्तर: ख) 3 mm²
Allowed drop 6.9 V gives R ≤ 6.9/20 = 0.345 Ω for the 60 m loop; A = ρL/R = 1.72 × 10⁻⁸ × 60/0.345 ≈ 3 × 10⁻⁶ m².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The hysteresis loop of a core material represents an energy loss of 500 J/m³ per cycle. For a core of volume 0.001 m³ on a 50 Hz supply, the hysteresis loss is:
सही उत्तर: क) 25 W
Loss = (energy per m³ per cycle) × volume × frequency = 500 × 0.001 × 50 = 25 W.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A coil of 200 turns is wound on a magnetic circuit of reluctance 4 × 10⁵ AT/Wb. Its self-inductance is:
सही उत्तर: ख) 0.1 H
L = N²/S = 200²/(4 × 10⁵) = 0.1 H.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A delta-connected load has unity-power-factor loads of 10 A in phases RY and YB only (phase BR open), on a balanced supply. The current in line Y is about:
सही उत्तर: घ) 17.3 A
Line Y carries the phasor difference of two 10 A phase currents 120° apart: |10∠0° − 10∠120°| = 10√3 ≈ 17.3 A (lines R and B carry 10 A each).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A parallel (tank) resonant circuit with Q = 50 draws 2 mA from the supply at resonance. The current circulating between L and C is about:
सही उत्तर: घ) 100 mA
At parallel resonance the circulating current is about Q times the line current: 50 × 2 mA = 100 mA (current magnification).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A Maxwell inductance–capacitance bridge balances with R₂ = 1 kΩ, R₃ = 500 Ω and C₄ = 0.2 μF. The unknown inductance (L = R₂R₃C₄) is:
सही उत्तर: घ) 0.1 H
L = R₂R₃C₄ = 1000 × 500 × 0.2 × 10⁻⁶ = 0.1 H.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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