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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Copper is divalent with atomic mass 63.5. Using F = 96500 C/mol, its electrochemical equivalent is about:
सही उत्तर: ख) 0.329 mg/C
z = (atomic mass/valency)/F = 31.75/96500 g/C ≈ 3.29 × 10⁻⁴ g/C = 0.329 mg/C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A balanced delta-connected resistive load takes power P from a three-phase supply. If one of the three supply lines is opened (e.g. by a blown fuse), the power drawn becomes:
सही उत्तर: ख) P/2
With one line open, one phase resistor R is directly across the remaining line voltage and the other two (2R) are in parallel with it: V²/R + V²/2R = 1.5V²/R, half of the original 3V²/R.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a 4-pole machine, one complete mechanical revolution of the rotor corresponds to:
सही उत्तर: ग) 720 electrical degrees
Electrical angle = (P/2) × mechanical angle = 2 × 360° = 720°.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 220 V DC motor has an armature resistance of 0.5 Ω. What external starting resistance limits the starting current to 40 A?
सही उत्तर: घ) 5 Ω
At start the back emf is zero, so 220/(0.5 + R) = 40 gives R + 0.5 = 5.5 Ω, i.e. R = 5 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 2 kW resistive heater works on a 230 V (RMS) sinusoidal supply. The peak value of its current is about:
सही उत्तर: क) 12.3 A
I_rms = 2000/230 ≈ 8.7 A and I_peak = √2 × 8.7 ≈ 12.3 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A battery of internal resistance 0.5 Ω drives a current of 2 A through an external 10 Ω resistor. Its emf is:
सही उत्तर: क) 21 V
E = I(R + r) = 2 × (10 + 0.5) = 21 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The total charge delivered by a 100 Ah battery when fully discharged is:
सही उत्तर: ख) 3.6 × 10⁵ C
1 Ah = 1 A × 3600 s = 3600 C, so 100 Ah = 360000 C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A conductor of cross-section 2.5 mm² carries a current of 10 A. The current density is:
सही उत्तर: ग) 4 A/mm²
J = I/A = 10/2.5 = 4 A/mm² (= 4 × 10⁶ A/m²).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Taking the resistivity of copper as 1.72 × 10⁻⁸ Ω·m, the resistance between opposite faces of a 1 m cube of copper is:
सही उत्तर: घ) 1.72 × 10⁻⁸ Ω
R = ρl/A = ρ × 1/1 = ρ numerically; resistivity is defined as the resistance of a unit cube.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The maximum energy density that can be stored in air just below its breakdown field of about 3 MV/m is about (ε₀ = 8.854 × 10⁻¹² F/m):
सही उत्तर: घ) 40 J/m³
u = ½ε₀E² = 0.5 × 8.854 × 10⁻¹² × (3 × 10⁶)² ≈ 39.8 J/m³.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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