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 the three-voltmeter method, a 10 Ω resistor is in series with an inductive load. The voltages are 50 V across the resistor, 100 V across the load and 130 V across the supply. The power taken by the load is:
सही उत्तर: घ) 220 W
P = (V² − V₁² − V₂²)/(2R) = (16900 − 2500 − 10000)/20 = 220 W.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A Lissajous figure on a CRO touches the horizontal (top) edge at 2 points and the vertical (side) edge at 1 point. If the horizontal input is 50 Hz, the vertical input frequency is:
सही उत्तर: घ) 100 Hz
f_y/f_x = (tangencies on a horizontal edge)/(tangencies on a vertical edge) = 2/1, so f_y = 100 Hz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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On a CRO, one cycle of a sine wave occupies 4 horizontal divisions with the time base set at 5 ms/div. The signal frequency is:
सही उत्तर: क) 50 Hz
Period = 4 × 5 ms = 20 ms, so f = 1/0.02 = 50 Hz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which type of instrument is best suited to measuring the RMS value of currents at radio frequencies?
सही उत्तर: ग) thermocouple (thermal) instrument
Heating depends on the true RMS value and the thermocouple element has very little inductance, so it works at high frequencies.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The guard terminal of an insulation resistance tester (megger) is used to:
सही उत्तर: क) divert surface leakage current away from the measuring circuit
Surface leakage current is routed through the guard so that only the volume (true insulation) current is measured.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An energy meter with a constant of 600 rev/kWh makes 61 revolutions while a steady 1 kW load runs for 6 minutes. Its percentage error is about:
सही उत्तर: घ) +1.67% (reads high)
Correct revolutions = 600 × 1 × 0.1 = 60; error = (61 − 60)/60 × 100 ≈ +1.67%, i.e. the meter runs fast.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The same three capacitors are connected first in star and then in delta across a three-phase supply. The kVAR supplied in delta is:
सही उत्तर: क) three times that in star
In delta each capacitor gets √3 times the voltage, and kVAR ∝ V², so delta gives 3 times as much.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Unity-power-factor loads in a four-wire star system draw 10 A, 20 A and 30 A in the three phases (balanced voltages). The neutral current is about:
सही उत्तर: क) 17.3 A
Adding 10∠0° + 20∠−120° + 30∠120° gives (−15) + j8.66, whose magnitude is √(225 + 75) ≈ 17.3 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A four-wire star system supplies resistive loads drawing 10 A in phase R, 10 A in phase Y and nothing in phase B (balanced voltages). The neutral current is:
सही उत्तर: ग) 10 A
Currents 10∠0° and 10∠−120° add to a phasor of magnitude 10 A, which returns through the neutral.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a balanced three-phase circuit, a single wattmeter with its current coil in line R and its pressure coil across lines Y and B reads W. The total reactive power is:
सही उत्तर: ख) √3 W
This connection reads V_L I_L sin φ, and the total reactive power is √3 V_L I_L sin φ = √3 W.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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