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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In circuits with magnetically coupled coils, the dot convention is used to show:
सही उत्तर: क) The relative polarity of the mutually induced voltages
Current entering a dotted terminal induces a voltage that is positive at the dotted terminal of the other coil.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A coil of 100 turns carrying 4 A produces a flux of 2 mWb linking all its turns. Its self-inductance is:
सही उत्तर: ख) 0.05 H
L = N phi / I = 100 x 0.002 / 4 = 0.05 H.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the thickness of the laminations in a transformer core is halved (all else unchanged), the eddy current loss becomes:
सही उत्तर: घ) One quarter of its original value
Eddy current loss is proportional to the square of lamination thickness, so halving thickness gives (1/2)^2 = 1/4.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the analogy between magnetic and electric circuits, magnetic flux corresponds to:
सही उत्तर: घ) Electric current
Flux = mmf / reluctance mirrors current = emf / resistance, so flux is the analogue of current.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Permeance, the reciprocal of reluctance, is measured in:
सही उत्तर: ख) Weber per ampere-turn
Permeance = flux / mmf, so its unit is Wb/AT (dimensionally the henry).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An iron ring has a mean length of 1 m, a cross-section of 10^-3 m^2 and relative permeability 1000. Its reluctance is about:
सही उत्तर: ग) 7.96 x 10^5 AT/Wb
S = l / (mu_0 mu_r A) = 1 / (4 pi x 10^-7 x 1000 x 10^-3) = 1 / (1.257 x 10^-6) = about 7.96 x 10^5 AT/Wb.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An electromagnet pole face of area 0.01 m^2 has a flux density of 1 T across the air gap. Using F = B^2 A / (2 mu_0), the lifting force is about:
सही उत्तर: क) 3.98 kN
F = 1^2 x 0.01 / (2 x 4 pi x 10^-7) = 0.01 / (2.513 x 10^-6) = about 3979 N.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A charge of 1 microcoulomb moves at 10^4 m/s at right angles to a magnetic field of 0.5 T. The force on it is:
सही उत्तर: ख) 5 x 10^-3 N
F = q v B = 10^-6 x 10^4 x 0.5 = 5 x 10^-3 N.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The magnetic flux density at 0.1 m from a long straight wire carrying 10 A in air is (mu_0 = 4 pi x 10^-7 H/m):
सही उत्तर: घ) 2 x 10^-5 T
B = mu_0 I / (2 pi r) = 2 x 10^-7 x 10 / 0.1 = 2 x 10^-5 T.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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One electron-volt (eV) of energy is equal to about:
सही उत्तर: क) 1.6 x 10^-19 J
1 eV is the energy gained by one electron charge moving through 1 V: 1.6 x 10^-19 C x 1 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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