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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A core of relative permeability 500 completely fills the magnetic path of a coil that was previously air-cored. Its inductance becomes:
सही उत्तर: क) 500 times larger
L = N^2 mu_0 mu_r A / l is directly proportional to mu_r.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Inserting a soft iron core into an air-cored solenoid carrying a fixed current:
सही उत्तर: ख) Greatly increases the magnetic flux
The iron's high permeability lowers the reluctance of the path, so the same mmf produces much more flux.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An electromagnetic relay is:
सही उत्तर: घ) An electrically operated switch worked by an electromagnet
Current in the relay coil magnetises a core that pulls an armature to open or close separate contacts.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Faraday constant, the charge carried by one mole of electrons, is approximately:
सही उत्तर: घ) 96,500 C
F = N_A x e = 6.022 x 10^23 x 1.602 x 10^-19 = about 96,485 C/mol.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a balanced three-phase, four-wire star system, power is measured with one wattmeter connected in one phase (current coil in the line, pressure coil between that line and neutral). The total power is:
सही उत्तर: ख) 3 times the wattmeter reading
The wattmeter reads one phase's power, and in a balanced system all three phases take equal power.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A single-phase motor draws 5 A from a 230 V supply and a wattmeter reads 920 W. The power factor is:
सही उत्तर: ग) 0.8
pf = P / (V I) = 920 / (230 x 5) = 920 / 1150 = 0.8.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two currents i1 = 10 sin(wt) A and i2 = 10 sin(wt + 120 degrees) A flow into the same wire. The peak value of their sum is:
सही उत्तर: क) 10 A
Phasor sum of two equal 10 A phasors 120 degrees apart = 2 x 10 x cos 60 = 10 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A voltage v = 10 + 10 sqrt(2) sin(wt) volts contains a DC part and an AC part. Its RMS value is about:
सही उत्तर: ख) 14.14 V
V_rms = sqrt(DC^2 + AC_rms^2) = sqrt(10^2 + 10^2) = sqrt 200 = 14.14 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a circuit, v = 200 sin(wt) V and i = 10 sin(wt - 60 degrees) A. The average power consumed is:
सही उत्तर: घ) 500 W
P = (Vm Im / 2) cos phi = (200 x 10 / 2) x cos 60 = 1000 x 0.5 = 500 W.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A pure coil has an inductive reactance of 314 ohm at 50 Hz. Its inductance is:
सही उत्तर: क) 1 H
L = X_L / (2 pi f) = 314 / 314 = 1 H.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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