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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Using four resistors of 4 Ω each, an equivalent resistance of 3 Ω is obtained by:
सही उत्तर: ग) connecting three in series and the combination in parallel with the fourth
(4 + 4 + 4) ∥ 4 = 12 × 4/16 = 3 Ω; the other arrangements give 1 Ω, 4 Ω and 4 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Three identical capacitors are connected first in series and then in parallel across the same DC voltage. The ratio of the energy stored in the series connection to that in the parallel connection is:
सही उत्तर: घ) 1 : 9
Series gives C/3 and parallel 3C; at the same V, energy ∝ C, so the ratio is (C/3) : 3C = 1 : 9.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A conductor has a temperature coefficient of resistance of 0.004 per °C referred to 0 °C. At what temperature will its resistance be twice its value at 0 °C?
सही उत्तर: क) 250 °C
R = R₀(1 + α₀t) = 2R₀ gives α₀t = 1, so t = 1/0.004 = 250 °C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Copper is divalent with atomic mass 63.5. Using F = 96500 C/mol, its electrochemical equivalent is about:
सही उत्तर: ख) 0.329 mg/C
z = (atomic mass/valency)/F = 31.75/96500 g/C ≈ 3.29 × 10⁻⁴ g/C = 0.329 mg/C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A balanced delta-connected resistive load takes power P from a three-phase supply. If one of the three supply lines is opened (e.g. by a blown fuse), the power drawn becomes:
सही उत्तर: ख) P/2
With one line open, one phase resistor R is directly across the remaining line voltage and the other two (2R) are in parallel with it: V²/R + V²/2R = 1.5V²/R, half of the original 3V²/R.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For a 4-pole machine, one complete mechanical revolution of the rotor corresponds to:
सही उत्तर: ग) 720 electrical degrees
Electrical angle = (P/2) × mechanical angle = 2 × 360° = 720°.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 220 V DC motor has an armature resistance of 0.5 Ω. What external starting resistance limits the starting current to 40 A?
सही उत्तर: घ) 5 Ω
At start the back emf is zero, so 220/(0.5 + R) = 40 gives R + 0.5 = 5.5 Ω, i.e. R = 5 Ω.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 2 kW resistive heater works on a 230 V (RMS) sinusoidal supply. The peak value of its current is about:
सही उत्तर: क) 12.3 A
I_rms = 2000/230 ≈ 8.7 A and I_peak = √2 × 8.7 ≈ 12.3 A.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A battery of internal resistance 0.5 Ω drives a current of 2 A through an external 10 Ω resistor. Its emf is:
सही उत्तर: क) 21 V
E = I(R + r) = 2 × (10 + 0.5) = 21 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The total charge delivered by a 100 Ah battery when fully discharged is:
सही उत्तर: ख) 3.6 × 10⁵ C
1 Ah = 1 A × 3600 s = 3600 C, so 100 Ah = 360000 C.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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