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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The increase in a conductor's AC resistance caused by the alternating magnetic field of a nearby current-carrying conductor is called:
सही उत्तर: ग) proximity effect
Proximity effect is due to the field of neighbouring conductors distorting the current distribution; skin effect is due to the conductor's own field.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A magnetic circuit has an iron path of reluctance 2 × 10⁵ AT/Wb and an air gap of reluctance 8 × 10⁵ AT/Wb. The fraction of the total mmf used up in the air gap is:
सही उत्तर: घ) 80%
In a series magnetic circuit the mmf divides in proportion to reluctance: 8/(8 + 2) = 80%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a Hall-effect experiment the sign of the Hall voltage is used to determine:
सही उत्तर: घ) whether the majority charge carriers are positive or negative
Positive and negative carriers drifting the same way are pushed to the same side but produce opposite Hall polarities, so the sign identifies the carrier type.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A long straight conductor of radius 1 cm carries 100 A distributed uniformly over its cross-section. The magnetic flux density inside it at 0.5 cm from the axis is (μ₀ = 4π × 10⁻⁷ H/m):
सही उत्तर: ख) 1 mT
Inside the conductor B = μ₀Ir/(2πR²) = 4π × 10⁻⁷ × 100 × 0.005/(2π × 10⁻⁴) = 1 × 10⁻³ T.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Coils of 0.2 H and 0.3 H with mutual inductance 0.1 H carry 2 A and 1 A respectively, with their fluxes aiding. The total magnetic energy stored is:
सही उत्तर: ख) 0.75 J
W = ½L₁I₁² + ½L₂I₂² + MI₁I₂ = 0.4 + 0.15 + 0.2 = 0.75 J (0.35 J if the fluxes opposed).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two coupled coils of 4 H and 6 H with mutual inductance 2 H are connected in parallel with their fluxes aiding. The equivalent inductance is about:
सही उत्तर: ख) 3.33 H
For parallel aiding, L = (L₁L₂ − M²)/(L₁ + L₂ − 2M) = (24 − 4)/(10 − 4) ≈ 3.33 H.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Three capacitors of 3 μF each are connected so that two are in parallel and the third is in series with that pair. The equivalent capacitance is:
सही उत्तर: क) 2 μF
The parallel pair gives 6 μF; in series with 3 μF: 6 × 3/(6 + 3) = 2 μF.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The loss tangent (tan δ) of a capacitor's dielectric is the ratio of:
सही उत्तर: ग) the resistive (loss) component of current to the capacitive component
In a real capacitor the current leads the voltage by (90° − δ); tan δ = I_R/I_C measures dielectric loss.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Capacitors of 2 μF (rated 100 V) and 4 μF (rated 100 V) are connected in series. The greatest DC voltage that can safely be applied across the combination is:
सही उत्तर: घ) 150 V
Equal charges mean the 2 μF capacitor takes 2/3 of the total voltage; limiting it to 100 V gives a total of 150 V (the 4 μF then has 50 V).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A coaxial cable has insulation of relative permittivity 4, and the ratio of outer to inner radius equals e (≈ 2.718). Its capacitance per metre is about (ε₀ = 8.85 × 10⁻¹² F/m):
सही उत्तर: ख) 222 pF/m
C per metre = 2πε₀ε_r/ln(b/a) = 2π × 8.85 × 10⁻¹² × 4/1 ≈ 2.22 × 10⁻¹⁰ F/m = 222 pF/m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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