प्राविधिक – इलेक्ट्रिकल, मेकानिकल र टेलिकम
प्राविधिक – इलेक्ट्रिकल, मेकानिकल र टेलिकम
Technical – Electrical, Mechanical & Telecom · ४,५०० प्रश्न
४,५०० प्रश्न उपलब्ध। मोड छान्नुहोस्:
इलेक्ट्रिकल र टेलिकम: 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 a three-phase four-wire distribution system, the fourth wire is the:
सही उत्तर: ख) neutral
The four wires are the three phases (R, Y, B) and the neutral, giving both 400 V and 230 V supplies.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In terms of phase quantities, the total power of a balanced three-phase load is:
सही उत्तर: क) 3 V_ph I_ph cos phi
Each of the three phases contributes V_ph I_ph cos phi.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A balanced delta load with 10 ohm resistance per phase is connected to a 400 V three-phase supply. The line current is about:
सही उत्तर: ग) 69.3 A
Phase current = 400 / 10 = 40 A; line current in delta = sqrt 3 x 40 = 69.3 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Three identical resistors connected in delta to a three-phase supply consume how many times the power they consume when connected in star to the same supply?
सही उत्तर: ख) 3 times
In delta each resistor gets the line voltage instead of V_L/sqrt 3, so power per resistor (V^2/R) increases 3 times.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Interchanging any two of the three supply lines to a three-phase induction motor:
सही उत्तर: ख) reverses its direction of rotation
Swapping two lines reverses the phase sequence, so the rotating magnetic field turns the other way.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The 'wattless' component of the current in an AC circuit is:
सही उत्तर: ग) I sin phi, the component in quadrature with the voltage
The component at 90 degrees to the voltage produces no average power, so it is called wattless (reactive) current.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An alternating current is i = 10 sin(100 pi t) amperes. Its value at t = 1/400 s is about:
सही उत्तर: क) 7.07 A
100 pi x 1/400 = pi/4 rad (45 degrees), and 10 sin 45 degrees = 7.07 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a circuit, v = 100 sin(wt) volts and i = 10 cos(wt) amperes. Which statement is correct?
सही उत्तर: क) The current leads the voltage by 90 degrees
cos(wt) = sin(wt + 90 degrees), so the current leads by 90 degrees, as in a pure capacitor.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A series RLC circuit with R = 20 ohm is at resonance across a 100 V supply. The current is:
सही उत्तर: क) 5 A
At resonance X_L cancels X_C, so Z = R and I = 100 / 20 = 5 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 100 kW load operates at 0.6 power factor lagging. The capacitor kVAR needed to raise its power factor to unity is about:
सही उत्तर: ग) 133 kVAR
Q = P tan phi; cos phi = 0.6 gives tan phi = 0.8/0.6 = 4/3, so Q = 100 x 4/3 = 133 kVAR, which must be cancelled.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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