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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Pin-type insulators are generally economical only up to about 33 kV; at higher voltages lines use:
सही उत्तर: ख) suspension (disc) insulators
Above about 33 kV pin insulators become too large and costly, so strings of suspension discs are used, adding units as voltage rises.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A string of 3 suspension insulator discs carries 33 kV in total, and the disc nearest the line conductor has 13.2 kV across it. The string efficiency is about:
सही उत्तर: घ) 83.3%
String efficiency = V/(n × V of the disc nearest the conductor) = 33/(3 × 13.2) ≈ 0.833 = 83.3%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Corona on high-voltage overhead lines is:
सही उत्तर: घ) ionisation of the air around the conductors, with a faint violet glow, hissing noise and power loss
When the surface field exceeds the breakdown strength of air, the air ionises, producing glow, noise, ozone and loss.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Bundled conductors (two or more sub-conductors per phase) are used on EHV transmission lines mainly to:
सही उत्तर: क) reduce corona loss and line reactance
Bundling increases the effective conductor radius, lowering the surface electric stress (corona) and the inductance per km.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An overhead conductor weighing 10 N per metre is strung between supports 200 m apart at the same level with a tension of 20 kN. The sag (S = wl²/8T) is:
सही उत्तर: क) 2.5 m
S = 10 × 200²/(8 × 20 000) = 400 000/160 000 = 2.5 m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Utilities often penalise industrial consumers who operate at a low power factor because a low power factor:
सही उत्तर: ख) makes the utility supply more current (kVA) for the same kW, increasing losses and equipment size
For the same active power, current ∝ 1/cos φ, so poor power factor raises I²R losses and the kVA capacity needed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A time-of-day (ToD) tariff encourages consumers to:
सही उत्तर: ग) shift their use away from peak hours by charging more for peak-time energy
Charging a higher rate in peak hours and a lower rate off-peak flattens the load curve and improves plant utilisation.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Under a block-rate tariff, the first 20 units cost Rs 4 each, the next 30 units Rs 7 each and further units Rs 9 each. The energy charge for 100 units is:
सही उत्तर: ख) Rs 740
20 × 4 + 30 × 7 + 50 × 9 = 80 + 210 + 450 = Rs 740.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 100 MW power station generates 438 GWh of energy in a year. Its plant capacity factor is:
सही उत्तर: घ) 0.5
Capacity factor = actual energy/(installed capacity × hours) = 438 000/(100 × 8760) = 0.5.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The diversity factor of a power system is normally:
सही उत्तर: ग) greater than 1
Individual maximum demands do not all occur at the same time, so their sum exceeds the system's maximum demand; hence diversity factor > 1.
💬 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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