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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The forward voltage drop across a conducting silicon diode is about:
सही उत्तर: क) 0.7 V
Silicon junctions have a cut-in voltage of about 0.6–0.7 V; germanium is about 0.3 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Fan regulators and light dimmers in AC circuits commonly use a TRIAC because it:
सही उत्तर: घ) can conduct in either direction and be triggered in each half-cycle
A TRIAC acts like two SCRs in inverse parallel with a common gate, giving phase control of both half-cycles of AC.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An ideal boost converter operates from 12 V with a duty ratio of 0.5. Its output voltage is:
सही उत्तर: ख) 24 V
For a boost converter V₀ = Vs/(1 − D) = 12/0.5 = 24 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An ideal buck (step-down) converter operating with a duty ratio of 0.4 from a 100 V DC supply gives an output voltage of:
सही उत्तर: ख) 40 V
For a buck converter V₀ = D·Vs = 0.4 × 100 = 40 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A cycloconverter converts:
सही उत्तर: ग) AC at one frequency directly into AC at another (usually lower) frequency
It synthesises lower-frequency AC directly from the supply without an intermediate DC link, used for large slow-speed drives.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A power-electronic converter that changes a fixed DC voltage into a variable DC voltage is called a:
सही उत्तर: ग) chopper
Choppers (DC–DC converters) switch the DC supply on and off to vary the average output; inverters give AC from DC.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A three-phase, six-pulse bridge rectifier is fed from a 50 Hz supply. The fundamental ripple frequency of its DC output is:
सही उत्तर: घ) 300 Hz
The output has 6 pulses per supply cycle, so the ripple frequency is 6 × 50 = 300 Hz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a single-phase bridge rectifier with input peak voltage Vm, the peak inverse voltage across each diode is:
सही उत्तर: क) Vm
In a bridge, each non-conducting diode is effectively across the supply, so its PIV is Vm (a centre-tap rectifier needs 2Vm).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A single-phase half-wave controlled rectifier feeding a resistive load from a supply of peak 311 V is fired at α = 60°. The average output voltage (Vm(1 + cos α)/2π) is about:
सही उत्तर: ख) 74 V
V_avg = 311 × (1 + 0.5)/(2π) ≈ 74.2 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For an SCR, the latching current is:
सही उत्तर: ग) greater than the holding current
Latching current is the minimum anode current needed just after triggering for the device to stay on; it is usually 2–3 times the holding current.
💬 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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